InTechOpen uses cookies to offer you the best online experience. By continuing to use our site, you agree to our Privacy Policy.

Engineering » Energy Engineering » "Sustainable Degradation of Lignocellulosic Biomass - Techniques, Applications and Commercialization", book edited by Anuj K. Chandel and Silvio Silvério da Silva, ISBN 978-953-51-1119-1, Published: May 15, 2013 under CC BY 3.0 license. © The Author(s).

Chapter 2

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

By Larissa Canilha, Rita de Cássia Lacerda Brambilla Rodrigues, Felipe Antônio Fernandes Antunes, Anuj Kumar Chandel, Thais Suzane dos Santos Milessi, Maria das Graças Almeida Felipe and Silvio Silvério da Silva
DOI: 10.5772/53832

Article top

Bioconversion of Hemicellulose from Sugarcane Biomass Into Sustainable Products

Larissa Canilha1, Rita de Cássia Lacerda Brambilla Rodrigues1, Felipe Antônio Fernandes Antunes1, Anuj Kumar Chandel1, Thais Suzane dos Santos Milessi1, Maria das Graças Almeida Felipe1 and Silvio Silvério da Silva1

1. Introduction

Sugarcane is main crop cultivated in countries like Brazil, India, China, etc. It plays a vital role in the economy of these countries in addition to providing employment opportunities [1]. Only in the 2012/13 Brazil harvest, for example, it was estimated that more than 602 million tons of sugarcane will be processed by the sugar-alcohol mills [2].

During the processing of sugarcane, the sugarcane straw (SS) is remained on field and do not presents suitable use. After the juice extraction from sugarcane stem, the fraction that is left over is called sugarcane bagasse (SB) [3]. Both residues (SB and SS) represent a sizeable fraction of agro-residues collected annually. The annual world production of sugarcane is ∼1.6 billion tons, which yields approximately 279 million metric tons (MMT) of SB and SS [1, 4].

SB is used as a source of heat and electricity in sugar producing mills while SL is openly burnt on the fields causing environmental pollution. The harnessing of both residues via biotechnological routes into value-added products (xylitol, organic acid, industrial enzymes, ethanol, etc) is much more likely to be complimentary than competitive in the near term without jeopardizing the food requirements [5, 6, 7]. Both residues (SB and SS) are principally constituted of cellulose, hemicellulose and lignin. Among these constituents, hemicellulose is of particular interest because of its unique properties and composition. In the last two decades of research has been witnessed the technological development for the hemicellulose depolymerization into its monomeric constituents, mainly xylose, and their subsequent conversion into value-added products via microbial fermentation [8, 9, 10]. Dilute acid hydrolysis is a well established process for hemicellulose depolymerization, however, inhibitory compounds of microbial metabolism are also formed and should be reduced/eliminated prior to using the liquid in the fermentation process [8, 9]. On the other hand, enzymatic conversion of hemicellulose, that requires cocktail of enzymes for its breakdown, is slow, costly and requires combinatorial mixture of specialized enzymes [9]. The recovered sugar solution after hemicellulose hydrolysis contains primarily pentose sugars and the fermentation of these pentosans is problematic. Only limited numbers of microorganisms that use pentose are known and the fermentation of pentose sugars at industrial scale is not established yet [10, 11]. Generally, pentose utilizing microorganisms have slow growth rate, low osmotolerance and have poor resistance against inhibitors. The microorganisms that use pentose more extensively explored in laboratories are Candida shehatae, Pichia stipitis, Pachysolen tannophilus (for ethanol production), C. utilis, C. intermedia, C. guilliermondii (for xylitol production) and Klebsiella oxytoca ATCC 8724, Bacillus subtilis, Aeromonas hydrophilia (for 2, 3-butanediol production) [8, 9, 12].

Rather than summarizing all the literature on hemicellulose bioconversion from sugarcane agro-residues, we aim to highlight in this chapter technological developments focusing hemicellulose hydrolysis, detoxification of hydrolysates and microbial fermentation of sugars into sustainable products.

2. Sugarcane, bagasse and straw

2.1. Structure of sugarcane

The sugarcane basically consists of stem and straw. Stem is the part normally associated with sugarcane (cleaned cane). It is the piece of cane plant between plantation level and end node from last stem. The sugarcane stem are crushed to obtain cane juice, which is subsequently used for sugar (sucrose) or alcohol (ethanol) production. Sugarcane bagasse (SB) is the left over residue from stems after extraction of juice. It is normally burned to supply all the energy required in the process [13]. Sugarcane straw (or trash) (SS) is composed by fresh leaves, dry leaves and tops available before harvesting. Fresh (green and yellow) leaves and tops are the part of cane plant between the top end and the last stalk node. Dry leaves are normally in brownish color [14]. The SS is also normally burnt in the field after the harvest of the crop [15]. Potential applications of the leaves include: 1) as a fuel for direct combustion; 2) as a raw material for conversion by pyrolysis to char, oil and/or gas; and 3) as a raw material for conversion by gasification and synthesis to methanol. Potential applications of the tops include: 1) as a ruminant feed, either fresh or dried; 2) as a substrate for anaerobic fermentation to methane production; and 3) after reduction in water content, for the three energy uses listed for cane trash. Figure 1 presents the scanning electronic microscopy (SEM) of SS and SB before pretreatment. In the Figures 1A and 1B the SS was amplified 500 and 10.000x which reveal the presence of some vacuoles in the structure, which is not common in SB (Figure 1C).


Figure 1.

SEM of sugarcane straw (A) 500x and (B) 1000x [16] and sugarcane bagasse (C) 500x (Chandel et al., unpublished work).

2.2. Physical and chemical compositions of sugarcane

Physically, sugarcane is constituted by four fractions, whose relative magnitude depends on the agro industrial process: fiber, non-soluble solids, soluble solids and water. The fiber is composed of the whole organic solid fraction, non-soluble in water, originally found in the cane's stalk, and characterized by its marked heterogeneity from the morphological point of view. The non-soluble solids, or the fraction that cannot be dissolved in water, are constituted mainly by inorganic substances (rocks, soil and extraneous materials) and it is greatly influenced by the conditions of the agricultural cane processing and harvesting type. Soluble solids, fraction that can be dissolved in water, are composed basically of sucrose as well as other small chemical components such as waxes [17].

Bagasse and straw (trash), which are the focus of second generation ethanol production, are lignocellulosic materials chemically composed by cellulose, hemicelluloses and lignin. According to some works in the literature, sugarcane bagasse of the Brazilian territory is quantitatively composed by 38.8-45.5% cellulose, 22.7-27.0% hemicellulose and 19.1-32.4% lignin (Table 1). Non-structural components of biomass namely ashes (1.0-2.8%) and extractives (4.6-9.1%) are the other substances that are part of the chemical compositional of bagasse. The ash content of bagasse is lower than the others crop residues, like rice straw and wheat straw (with approximately 17.5 and 11.0% of this compound, respectively) and the bagasse is considered a rich solar energy reservoir due to its high yields and annual regeneration capacity (about 80 t/ha) in comparison with others agricultural residues, like wheat, grasses and tree (1, 2 and 20 t/ha, respectively) [3]. The bagasse also can be used as a raw material for cultivation of microorganisms for the production of value-added products such as xylitol and ethanol. Due to these and others advantages the bagasse is not only a sub-product of sugar industry, but it is a co-product with high added-value [3].

As can be seen in the Table 1, the chemical compositions of sugarcane bagasse samples varied widely. In fact, it is impossible to compare the composition of samples from different origins, performed by different laboratories and that do not use the same methods. Furthermore, factors like plant genetics, growth environment and processing conditions also influence the compositional analysis [18].

The large variation in the values of chemical components also is observed for the sugarcane straw, that it is composed approximately by 33.3-36.1% cellulose, 18.4-28.9% hemicellulose, 26.1-40.7% lignin (Table 2). Ashes (2.1-11.7%) and extractives (5.3-11.5%) are also present on the sugarcane straw composition.

When mechanically harvested, and depending on the harvesting technology applied, the range of straw that is collected and transported to the mill together with the stalks is 24% to 95% of the total trash available [19]. The amount of trash from sugarcane harvesting depends on several factors such as: harvesting system, topping, height, cane variety, age of crop (stage of cut), climate, soil and others. The average stalks yield per hectare was estimated to 83.23 tons/ha over an average of 5 seasons (cuts), resulting average availability of trash of 11.98 tons/ha (dry basis) [20].

Component (%) Reference

Table 1.

Chemical composition (% w/w, dry basis) of Brazilian and worldwide sugarcane bagasse samples reported in the literature

[i] - *Extractives-free basis; #Lignin and others

[ii] - Extracting solvents: 1dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 2none; 3water and ethanol; 4ethanol; 5none; 6none; 7not described

Component (%) Reference
Lignin26.240.726.231.8# 26.118.0

Table 2.

Chemical composition (% w/w, dry basis) of Brazilian and Indian sugarcane straw samples reported in the literature

[i] - *Extractives-free basis; #Lignin and others

[ii] - Extracting solvents: 1ethanol; 2dichloromethane, ethanol: toluene (1:2), ethanol, hot water; 3water; 4none; 5none; 6none

From the technological viewpoint, sugars that are present in the cellulosic (glucose) and hemicellulosic (xylose, arabinose, glucose, mannose and galactose) fractions representing the substrates that can be used in fermentative process for production of some sustainable products such as xylitol, butanediol, single cell protein, ethanol and xylitol. However, the close association between the three major fractions (cellulose, hemicellulose and lignin) of the lignocelulosic materials, like bagasse and straw, causes difficulties for the recovery of these substrates in the form of monomers with high purity. Therefore, to use these three constituents it is required a selective separation of each fraction by pretreatment techniques, delignification and hydrolysis, involving the breakdown of hemicellulose-lignin-cellulose complex [21].

3. Methods of separation of hemicellulose from cellulignin complex

The lignocellulosic materials are renewable resources which can be used to obtain sustainable products as well as value-added biomolecules [31]. However, cellulose, hemicellulose and lignin are arranged to form a highly recalcitrant structure [32], hindering the availability of carbohydrates for fermentation processes, representing a high barrier for the bioconversion of lignocellulosic materials [33]. Through a pretreatment process, the biomass components can be separated, releasing fermentable sugars such as xylose, arabinose and glucose and making the cellulose more accessible to the action of cellulolytic enzymes [34, 35]. This step is one of the most expensive step of biomass processing, thus, studies to lower the cost are extremely important [35].

According to Brodeur et al. [36], the typical characteristics that must be attained in a pretreatment process are: production of highly digestible solids that enhances sugar yields during enzyme hydrolysis; avoid the degradation of sugars; minimize the formation of inhibitors; recover the lignin for conversion into valuable co-products. Pretreatment process should be cost effective and environment friendly. All these features are considered in order that pretreatment results balance against their impact cost on downstream processing steps and the trade-off with operational cost, capital cost and biomass cost [37]. The pretreatments methods can be divided into physical, chemical, physic-chemical and biological [38]. Some methods of pretreatments as well as their advantages and disadvantages are shown in the Table 3.

Different types of biomass (woody plants, grasses, agricultural crops, etc) has different contents and proportions of cellulose, hemicellulose and lignin which determine the digestibility of the biomass [37]. There is not a universal pretreatment process for all biomass. Depending on the process and conditions used, hemicellulose sugars may be degraded to weak acids, furan derivates and phenolics that inhibit the fermentation process, leading to lower yields and productivities of the desired product [8]. Thus, the method of pretreatment used will depend on the type of raw material used, the objective of the process (the constituent to be degraded) and the product to be obtained, which will directly affect the cost benefit.

Process Advantages Disadvantages Solubilized Fraction References
Hemicel. Cel. Lignin
Physical Pretreatments
Millingball milling provides the reduction of particles size and breaks down the structure of lignocellulosic materials- environment friendly
- chemical addition is not required
- inhibitors are not produced
- high power
- high energy costs
Alteration in structure[23]
Pyrolysistreatment with temperatures higher than 300ºC- fast degradation of cellulose into H2, CO and residual char- high temperature
- ash production
Physic-Chemical Pretreatments
Steam Explosion or hydrothermalstructure compounds breakdown by heat addition in form of steam and forces by the moisture expansion- needs few or no chemical addition
- environment friendly
- inhibitors productionX[41]
Ammonia Fiber Explosion (AFEX)expose the lignocellulosic material with ammonia to high temperature and pressure followed by a fast pressure release- inhibitors are not produced
- simple process
-short time process
- cost of ammonia
- ammonia recovery
- depending of lignin content
CO2 Explosionformation of carbonic acid and increase the hydrolysis rate of substrates- more cost effective
- inhibitors are not produced
- hard operation methodXX[40]
Chemical Pretreatments
Acid Pretreatmentdilute-acid hydrolysis of the lignocellulosic material- low and medium temperatures- equipment corrosion
- inhibitors production
Alkaline Pretreatment
delignification process employing bases such as sodium hydroxide, calcium hydroxide (lime), etc- low temperature
- low pressure
- long processing time
- environment pollution
Ozonolysisthe ozone incorporates conjugated double bonds and functional groups with high electron densities- removal of lignin
- inhibitors are not produced
- ambient temperature and pressure
- large amount of ozone is required
- expensive process
Organosolvsimultaneous process of hydrolyses and delignification catalyzed by solvents and diluted acid solution- facilitates the enzyme access
- needs few chemical addition
- low waste generation
- expensive processX[47]
Wet Oxidationoccurs in the presence of oxygen or catalyzed air, sodium carbonate is the preferred catalyst- released sugars without generation of inhibitors- expensive process
- high pressure
Biological Pretreatments
Microorganismmodification of the chemical composition and/or structure of lignocellulosic materials employing microorganisms- environment friendly- low efficiency
- considerable loss of carbohydrates
- long processing time

Table 3.

Advantages and disadvantages of different methods of pretreatment

[i] - Hemicel.: hemicellulosic fraction; Cel.: cellulosic fraction; X: solubilized fraction by the pretreatment

4. Hemicellulosic fraction

4.1. Structure of hemicellulose

Hemicellulose differs substantially from cellulose to be amorphous, which makes it more easily hydrolyzed than cellulose [49]. The hemicellulosic fraction reaches 40% of lignocellulosic material and acts as substance of reserve and support. This fraction presents branched structure composed by pentoses (D-xylose and L-arabinose), hexoses (D-galactose, D-mannose and D-glucose) and small amounts of acetic and uronic (D-glucuronic, D-4-O-methylglucuronic and D-galacturonic acids) acids [8, 21]. Other sugars such as L-rhamnose and L-fucose may also be present in small amounts. Xylose is the main carbohydrate present in the hemicellulosic fraction, representing about 80% of total sugars [35, 50].

The heterogeneous structure of hemicellulose with a low polymerization degree makes it interesting fraction for fermentation process. The open three-dimensional conformation of hemicellulose favors the diffusion of the catalyst in the molecule, providing a better yield of hydrolysis in mild conditions [51, 52].

The hemicellulosic fraction can be removed of lignocellulosic materials by some type of pretreatments, summarized in the Table 3, liberating sugars, mainly xylose, that subsequently can be fermented to sustainable products such as xylitol, butanediol, single cell protein and ethanol [24, 27].

4.2. Methods of detoxification of hemicellulosic hydrolysates

When the lignocellulosic matrix is breakdown by different types of pretreatments, particularly by dilute acid process, undesired compounds that are toxic for microbial metabolism are liberated and/or formed in addition of sugars. These products can be divided into three groups according to their origin: derived from sugars (furfural and 5-hydroxymethylfurfural), lignin derivatives (phenolics i.e. vanillin, p-hydroxybenzaldehyde, lignans, etc.) and weak acids (acetic, formic and levulinic) [53]. Several studies have shown that these byproducts generated during the hydrolysis of the hemicellulose fraction from different materials affect negatively the microbial metabolism, hindering the conversion of sugars in some products of interest [53, 54, 55].

Several chemical, physical and biological methods have been used for removing these byproducts present in the hemicellulosic hydrolysates. Some detoxification methods as well as their advantages and disadvantages are summarized in the Table 4.

4.3. Products from hemicellulose

Hemicelluloses have a wide variety of applications. They can be hydrolyzed into hexoses (glucose, galactose, and mannose) and pentoses (xylose and arabinose), can be transformed into fuel ethanol and other value-added products such as 5-hydroxymethylfurfural (HMF), xylitol, ethanol, butanediol, butanol, etc. In addition, hemicelluloses also can be converted into various biopolymers, like polyhydroxyalkanoates (PHA) and polylactates (PLA).

In industrial applications, hemicelluloses are used to control water and the rheology of aqueous phases. Thus, they may be used as food additives, thickeners, emulsifiers, gelling agents, adhesives and adsorbents [71]. According to Peng et al. [72], hemicelluloses have also been investigated for their possible medical uses such as ulcer protective [73], antitussive [74], immunostimulatory [75] and antitumor properties [76]. For example, xylooligosaccharides have been shown to have economic utilization in the pharmaceutical industry for applications such as treating viral and cancer processes in the human body [77, 78].

Process Advantages Disadvantages References
Physical Methods
removes toxic compounds by evaporation in a vacuum concentrator based on the volatility- reduces volatile compounds as acetic acid, furfural, and vanillin- increasing the nonvolatile toxic compounds as extractives[56]
Membranemembranes have surface functional groups attached to their internal pores, which may eliminate metabolic inhibitors- avoids the need to disperse one phase and minimize the entrainment of small amounts of organic phase- high cost
- selective removal of inhibitors
Physic-Chemical Methods
Ion Exchange Resinresins change undesirable ions of the liquid phase to be purified by saturating of functional groups of resins- can be regenerated and reused
- remove lignin-derived inhibitors, acetic acid and furfural
- does not cause high sugars loss
- high pressure
- long processing time
- possible degradation of fragile biological product molecules
- difficult to scale-up
Overlimmingincrease of the pH followed by reduction- precipitate toxic compounds- high sugars loss
- filtration complexity
Activated Charcoaladsorption of toxic compounds by charcoal which is activated to increase the contact surface- low cost
- remove phenolics and furans
- minimizes loss of sugars
- filtration complexity[60]
Extraction with Organic Solventsmix of liquid phase to be purified and a organic solvent. The liquid phase is recovered by separation of two phases (organic and aqueous)- recycling of solvents for consequent cycles
- remove acetic acid, furfural, vanillin, 4-hydroxybenzoic acid and low molecular weight phenolics
- high cost
- long processing time
Vegetable Polymerbiopolymers are composed by tannins with astringent properties that flocculate inhibitors compounds- low cost
- biodegradable
- minimizes loss of sugars
- reducing toxic compounds
- cell death when the tannin
content is high
- significant volume loss
Biological Methods
Microorganismspecific enzymes or microorganisms that act on the inhibitors compounds present in hydrolysates and change their composition- low waste generation
- environmental friendly
- less energy requirements
- long processing time[56]

Table 4.

Advantages and disadvantages of different detoxification methods of hemicellulosic hydrolysate

Arabinoxylans are used as emulsifiers, thickeners, or stabilizers in the food, cosmetic, or pharmaceutical industries. Glucomannans are used in the food industry (as caviar substituent), whereas arabinogalactans have applications in the mining (for processing of iron and copper ores) or pharmaceutical industry (as a tablet binder or emulsifier). 4-O-methylglucuronoxylan is a water absorption agent and also presents antitumor activity [71].

4.3.1. Xylose and glucose

The D-xylose (C5H10O5) is the main carbohydrate found in the hemicellulose fraction of sugarcane bagasse and straw. It is used as a sweetener for diabetics [79], as non-cariogenic sweetener [80], to enhance the flavor of food made from beef and poultry [81], to prepare marinades and baked [81] and as substrate in fermentation processes to produce different products, such as penicillin, biodegradable polymers and xylitol [50, 82]. Monomeric xylose from hemicellulose has a selling price of ~$1.2/kg [83]. It is known that in industrial scale, xylose is obtained from lignocellulosic materials rich in xylan. These materials are hydrolyzed in the presence of dilute acids. Then, the hemicellulose hydrolysates are purified, in order to remove the byproducts generated during the hydrolysis of hemicellulose. After the purification steps, xylose is recovered of purified media by crystallization [84].

D-glucose is also found in the hemicellulose fraction of sugarcane bagasse and straw and can be obtained by hydrolysis of cellulosic materials. Some compounds that are obtained from glucose fermentation are alcohols (ethanol, isopropanol, butanol, 2,3-butanediol, glycerol), carboxylic acids (acetic acid, propanoic acid, lactic acid, gluconic acid, malic acid, citric acid) and other products such as acetone, amino acids, antibiotics, enzymes and hormones [85].

4.3.2. 5-Hydroxymethylfurfural and levulinic acid

5-Hydroxymethylfurfural (HMF) (C5H4O2), which is derived from the hexoses (6-carbon sugars) present in the hemicellulose, is produced by steam treatment followed by dehydration [85, 86, 87]. HMF is an intermediate in the production of levulinic acid from 6-carbon sugars in the biofinery process. HMF is very useful not only as intermediate for the production of the biofuel, dimethylfuran (DMF) and other molecules, but also for important molecules such as levulinic acid, 2,5-furandicarboxylic acid (FDA), 2,5-diformylfuran (DFF), di-hydroxymethylfuran and 5-hydroxy-4-keto-2-pentenoic acid [88]. Glucose is still utilized in industry for the preparation of HMF because of its price lower than fructose [89].

Levulinic acid (4-oxopentanoic acid) (C5H8O3) is a valuable platform chemical due to its specific properties. It has two highly reactive functional groups that allow a great number of synthetic transformations. Levulinic acid can react as both a carboxylic acid and a ketone. The carbon atom of the carbonyl group is usually more susceptible to nucleophilic attack than that of the carboxyl group. Due to the spatial relationship of the carboxylic and ketone groups, many of the reactions proceed, with cyclisation, to form heterocyclic type molecules (for example methyltetrahydrofuran). Levulinic acid is readily soluble in water, alcohols, esters, ketones and ethers. The worldwide market has estimated the price of $ 5/kg for pure levulinic acid [86].

4.3.3. Furfural and formic acid

Furfural (2-furaldehyde) and its derivatives, furfuryl alcohol, furan resins, and tetrahydrofuran, are produced in many countries from corn cobs, wheat and oat hulls, and many other biomass materials [90]. Furfural, which is derived from the pentoses (five-carbon sugars) present in hemicellulose, is produced by steam treatment followed by dehydration with hydrochloric or sulfuric acid [87, 90]. The market price of furfural was approximately $1/kg compared with prices in 1990 of $1.74/kg for furfural and $1.76/kg for furfuryl alcohol [83, 86]. The most important furfuryl alcohol is used to produce furan resins for foundry sand binders. Tetrahydrofuran is made by the decarbonylation of furfural with zinc-chromium-molybdenum catalyst followed by hydrogenation. It is also made by the dehydration of 1,4-butanediol [87]. Other uses for furfural, such as production of adiponitrile, might be found if furfural prices were reduced by expanded production [90].

Formic acid (methanoic acid) is an important organic chemical which is widely used in industries. Recently, it received renewed attraction to be used as environmentally benign storage and transportation medium for hydrogen, the clean energy in future. Extensive studies have shown that hydrogen and CO2 could be quickly and efficiently generated by the decomposition of formic acid by hydrothermal reaction or catalyst reaction. Also, some researchers have demonstrated that formic acid has the potential to direct power fuel cells for electricity generation and automobiles [91]. It is used extensively as a decalcifier, as an acidulating agent in textile dyeing and finishing, and in leather tanning. It is also used in the preparation of organic esters and in the manufacture of drugs, dyes, insecticides, and refrigerants. Formic acid can also be converted to calcium magnesium formate which can be used as a road salt. The current market price of formic acid is $0.16/liter [86].

4.3.4. Xylitol

Xylitol is a polyol of five carbons (C5H12O5) easily found in nature in many fruits and plants. Among them, the yellow plum is the vegetable that contains highest level of xylitol [92]. This polyol is an intermediate metabolite in the carbohydrate metabolism in mammals, with an endogenous production followed by assimilation of 5-15g per day in a normal adult. Xylitol is widely used as a sweetener by diabetics due to its slow adsorption and entrance in pathways which is independent of the insulin and does not contribute in rapid change of blood glucose levels [93].

This polyol, with anti-cariogenic properties, is employed in foods, dental applications, medicines and surfactants [94, 95]. In the dental applications, the use of xylitol reduces the salivary flow, reduce gingivitis, stomatitis and lesions to poorly fitted dentures. If used in toothpaste, its action enhances the action of sodium fluoride and chlorhexidine, increasing the concentrations of xylitol 5-P [96]. For human diet, the Food and Drug Administration classifies this product as “GRAS” - “Generally Recognized as Safe” [97].

At large scale, xylitol is produced by chemical reduction of xylose derived mainly of wood hydrolysates. This process consists in steps of acid hydrolysis of the vegetal material, hydrolysate purifications and crystallization of xylitol [92]. However, there are disadvantages in the chemical production such as the use of high temperature and pressure in the process and the purification steps with low efficiency and productivity [52]. In this context, the biotechnological production of xylitol from hemicellulosic hydrolysates is a promising process with great economic interest. This process can add value to the lignocellulosic residues, like sugarcane bagasse and straw, promoting a complete utilization of these materials, using the cellulosic and hemicellulosic fractions to obtain xylitol and others value-added bioproducts [98]. Among the microorganisms that produce xylitol, yeast, particularly the genus Candida, Pichia, Debaryomyces are the most employed due to their ability to convert xylose to xylitol, with significant yields [99]. Xylitol can be produced through microbial transformation reactions by yeast from D-xylose, or by both yeast and bacteria from D-glucose [100]. D-xylose can also be directly converted into xylitol by NADPH-dependent xylose reductase [101].

Considering xylose fermentation by yeasts, the main factors that should be controlled are: substrate concentration, cellular concentration, the presence of inhibitors, aeration flow, adaptation of the microorganism to the hydrolysate, temperature and pH [102, 103]. It can be found many works in the literature where these factors were studied extensively using the hemicellulosic hydrolysates obtained from different lignocellulosic materials. From sugarcane bagasse hemicellulosic hydrolysate, for example, Carvalho et al. [61] reported the production of 19.2 g/L of xylitol by Candida guilliermondii; Santos et al. [104] achieved 18 g/L of xylitol with a bioconversion yield of 0.44 g/g employing a fluidized bed reactor operated in semi-continuous mode with the same yeast; and recently, Prakash et al. [105] produced xylitol, with a yield and volumetric productivity of 0.69 g/g and 0.28 g/L.h, respectively, using Debaryomyces hansenii.

The world xylitol production exceeds 10,000 tons per year and is directed mainly to the food, pharmaceutical and cosmetics [106]. The American xylitol market is estimated at $159 million for 2012 while it expected $400 million to $500 million for global market [107]. From the Figure 2, it can be seen the average annual prices of xylitol from 1995 to 2007. Xylitol price has decreased over last decades until 2007 (Figure 2), however since 2009, the price of xylitol has increased to $4-5/kg [108].


Figure 2.

Xylitol price profile from 1995 to 2007 (Source: adapted from reference [109]).

4.3.5. Ethanol

Currently, the world has the prospect of a significant increase in demand for ethanol. The use of this fuel is concentrated on a global scale in power generation, in its mixture with gasoline or simply dehydrated, being a considerable product in the global energy matrix [110].

The first generation ethanol production consists in conversion of hexose sugars to ethanol, and it is relatively simple and usually performed in three steps: acquisition of fermentable sugars, fermentation of sugars by microorganisms and separation and purification of ethanol, usually carried out by distillation, rectification and dehydration [111]. Microorganisms such as Saccharomyces cerevisiae consumes directly the sucrose present in sugarcane juice producing ethanol. However, in the long scenario, the use of juice or molasses to produce ethanol will not be able to supply the increasing demand.

Biofuels from renewable sources, such as second generation ethanol production from lignocellulosic materials (bagasse and straw), may represent a sustainable alternative to environmental and social problems caused due to the extensive use of fossil fuels [112]. The process for second generation ethanol requires three steps: pretreatment of lignocellulosic materials, to make the hemicellulose sugars and cellulose more accessible, fermentation of sugars and separation and purification of ethanol [111]. Although it is an eminent perspective, the development of this technology requires some additional challenges. The production of ethanol from lignocellulosic biomass can increase the productivity of ethanol per hectare of sugar cane planted [113], without increasing the cultivated area in the same proportions, not competing with food production for land use [112].

S. cerevisiae is the most common microorganism used for ethanol production from hexose sugars, but it is unable to produce ethanol from pentoses such as xylose. Among the microorganism that can assimilate pentose sugars such as xylose, yeasts have shown more ethanol yield and productivity than bacteria and fungi [114]. There are some naturally yeast which ferments xylose to ethanol, among them, Pichia stipitis [116] and Candida shehatae [117] are the most employed in bioprocess.

Considering the process for production of second generation ethanol, sugarcane bagasse is reported as one of most used lignocellulosic materials, and among the microorganisms used for xylose conversion, P. stipitis yeast (taxonomic classification has been changed to Scheffersomyces stipitis [118]) is widely used. For example, from sugarcane bagasse hemicellulosic hydrolysate, Canilha et al. [119] reported 7.5 g/L, 0.30 g/g and 0.16 g/L.h of ethanol production, yield and productivity, respectively, using hydrolysate treated with ion exchange resins as a medium of fermentation for ethanol production by P. stipitis DSM 3651 while Hande et al. [120] obtained 0.45 g/g using hydrolysate treated by neutralization and activated charcoal adsorption as a medium of fermentation for ethanol production by Pichia strain BY2. Other yeasts can be found in studies for ethanol production from sugarcane hemicellulosic hydrolysate. For example, Chandel et al. [121] observed maximum ethanol yield (0.48 g/g) from ion exchange detoxified hydrolysate followed by use activated charcoal, by C. shehatae NCIM 3501 and Cheng et al. [122] obtained 19 g/L ethanol, yield of 0.34 g/g and productivity of 0.57 g/L.h when used a batch culture with pretreated hydrolysate as substrate for Pachysolen tannophilus DW06. For sugarcane straw, the ethanol production is only from cellulosic fraction. For example, Krishnan et al. [4] verified an ethanol production about 34–36 g/L using the recombinant S. cerevisiae (424A LNH-ST) from the bagasse and straw pretreated by ammonia fiber expansion method (AFEX). Sindhu et al. [123] observed the ethanol production of 11.365 g/L using S. cerevisae yeast from leaves pretreated with dilute acid hydrolysis followed by enzymatic saccharification with cellulases.

Regarding the world ethanol scenario, a regular increase in the production has been observed (Figure 3). The Americas are the largest producer continent of ethanol. The United States of America is the largest producer country of ethanol with production levels over 51 billion liters (13.5 U.S. gallons) in 2011 [124].


Figure 3.

World Annual Ethanol Production since 2006 (Source:[125]).

4.3.6. Butanol

Biobutanol, a four carbon primary alcohol (butyl alcohol-C4H10O), is second generation alcoholic fuel with a higher energy density and lower volatility as compared to ethanol in addition to its existing applications as a solvent [126, 127]. The primary use of butanol is as an industrial solvent in the manufacturing of products such as lacquers and enamels. Butanol can be used directly in any gasoline engine without modification and/or substitution, because it has several similar characteristics to gasoline, besides being compatible with ethanol blending may improve the blending of gasoline with ethanol [128]. It can be produced through processing of domestically grown crops, such as corn and sugar beets, and other biomass residues [128].

Production of butanol by using fermentation to replace the chemical process depends largely on the availability of inexpensive and abundant raw materials and efficient bioconversion of these materials. The producers strains of biobutanol which have been extensively studied are Clostridium sp. [126, 127] and genetically engineered E. coli [129, 130]. Studies to determined the recovery of biobutanol from fermentation broth (dry corn and wet corn milling) whey permeate and molasses) by distillation showed that it was not economical when compared with butanol derived from the current petrochemical route [131]. The use of lignocellulosic substrates in combination with developed process technologies is expected to make the production of biobutanol economically viable [132].

4.3.7. Butanediol

2,3-Butanediol (2,3-BDL), also known as 2,3-butylene glycol, is a valuable chemical feedstock because of its application as a solvent, liquid fuel, and as a precursor of many synthetic polymers and resins. One of its well known applications is the formation of methyl ethyl ketone, by dehydration, which can be used as a liquid fuel additive [8].

Butanediol is produced during oxygen-limited growth, by a fermentative pathway known as the mixed acid-butanediol pathway [133]. The 2,3-BDL pathway and the relative proportions of acetoin and butanediol serve to maintain the intracellular NAD/NADH balance under changed culture conditions. All of the sugars commonly found in hemicellulose and cellulose hydrolysates can be converted to butanediol, including glucose, xylose, arabinose, mannose, galactose, and cellobiose. The theoretical maximum yield of butanediol from sugar is 0.50 kg per kg. With a heating value of 27,200 J/g, 2,3-BDL compares favorably with ethanol (29,100 J/g) and methanol (22,100 J/g) for use as a liquid fuel and fuel additive [134]. Hexose and pentose can be converted to 2,3-BDL by several microorganisms including Klebsiella [135], Aeromonas [136], Bacillus [137], Paenibacillus [138], Serratia, Aerobacter [139] and Enterobacter [140].

4.3.8. Biopolymers

The use of plastics is consistently increasing in the society due to its advantages such as low cost and durability, and the replacement of conventional materials such as paper and glass [141]. However, these materials have xenobiotic and recalcitrant nature, having an extremely long degradation rate [142, 143]. Besides its slow degradation, the accumulation of plastic is a major risk to marine animals. When is landfilled, is more difficult to occurs the process of decomposition and when it is incinerated, causes the release of several toxic compounds [144]. Due to the increasing demand of plastics and its incorrect disposal, these materials have become a major environmental problem. An alternative to trying to solve this rising problem is the replacement of conventional plastics for biodegradable plastics. Biodegradable plastics are natural biopolymers that are synthesized and catabolized by microorganisms and are made from renewable resources and do not lead to the depletion of finite resources [145, 146]. Among bioplastics, polyhydroxyalkanoates (PHA) and polylactates (PLA) got significant attraction. The PHA's are typically accumulated by bacterial via intra or extracellular while PLA is produced by polymerizing lactic acid via microbial fermentation [147].

For replacement of the conventional plastic, biodegradable plastic is a feasible option. However, it is necessary that the price of biopolymers should be competitive [148]. The cost of production is directly linked to the type of microorganism and the substrate employed. The strain used should have a high specific growth rate, using low cost substrates and a high conversion factor of substrate in PHA [144]. The selection of the proper raw material for biopolymer production has an additional impact on the ecological pressure of the entire process [148]. Renewable sources of polymeric materials offer an answer for sustainable development of economically and ecologically attractive technology [149, 150].

Sugarcane biomass represents an enormous reserve of renewable carbon source, which has the potential to be utilized as a feedstock for the production of biodegradable polymers. For instance, using sugarcane bagasse hydrolysate, Yu and Stahl [151] investigated the simultaneous detoxification and PHA production by the bacterium Ralstonia eutropha and accumulated PHA at a rate of 57 wt% of cell mass despite the large index of inhibitors. Silva et al. [152] studied the biopolymer production by Burkholderia cepacia IPT 048 and B. sacchari IPT 101 from sugarcane bagasse hydrolysate and obtained polymer contents and yields reached, respectively, 62% and 0.39 g/g with strain IPT 101 and 53% and 0.29 g/g with strain IPT 048.

4.3.9. Single cell protein

To create a balance between food versus fuel production from lignocellulosic residues, adequate land use, judicious usage of grain and corn/cane crop residues is essential [153]. Mathews et al. [153] presented a sugarcane ‘feed+fuel’ biorefinery model, which produces bioethanol and yeast biomass, a source of single-cell protein (SCP), that can be used as a high-protein animal feed supplement. The yeast SCP, which is synthesized as a part of the process of producing cellulosic bioethanol from sugarcane can be used as a supplement for grass in the feed of cattle grazing on pasture and thereby potentially release land for increased sugarcane production, with minimal land use change effects.

The production of SCP by growing microorganisms on organic wastes and its use in animal feed has a long history. Protein as an animal feed supplement has long been viewed as a potentially very significant development, with much discussion devoted to the topic of microbial SCP since the 1970s. The grounds for the intense interest in SCP is that feedstocks, in the form of agricultural and organic wastes are plentiful, and the rate of growth of microorganisms producing SCP is prodigious. Whereas a soybean crop is harvested after 1 season of growth, microorganisms double their cell mass within hours [154]. According to Tanaka et al. [155] the production of single-cell protein (SCP) from lignocellulosic materials needs four steps: (1) physical and chemical pretreatments; (2) cellulase production; (3) enzymatic hydrolysis; and (4) assimilation or fermentation of holocellulose. For each step the following topics need to be considerate: (1) effect and mode of action of each pretreatment; (2) optimization of culture media and operating conditions, and application of mutation, protoplast fusion and gene recombination; (3) elucidation of kinetics of cellulase reaction, and methods of immobilization, stabilization and recovery of cellulases; and (4) examples of SCP production by several types of cultivation and treatment of lignin. According to Zadrazil et al. [156] in order to convert a lignocellulosic material to obtain a more nutritive product, it is necessary to choose a microorganism or a microbial complex capable of synthesizing proteins with high nutritional value and, in the case of use of a substrate that has not been subjected to a previous hydrolysis step, able to degrade selectively the lignin present in the substrate. The lignocellulosic wastes can be fermented directly or they can be previously hydrolyzed chemically. Several reports have shown the application of substrates chemically pre-hydrolyzed for rapid protein enrichment by microbial fermentation. For example, Pessoa et al [157] hydrolyzed sugarcane bagasse using diluted sulphuric acid and the hydrolysate was fermented with Candida tropicalis. This process resulted in a 31.3% increase in protein content after 5 days of fermentation. However, for non-ruminant animals, which are not able to metabolize the natural fibers that comprise the bulk of lignocellulosic wastes, the bioconversion process must aim to transform these fibers into digestible components such as protein and sugars (mono- and disaccharides) as well as vitamins and minerals.

5. Conclusion and future recommendations

Sugarcane bagasse (SB) and straw (SS) constitute a sizeable fraction of agro-residues in many countries. Brazil is the largest producer of sugarcane residues in the world. Hemicellulose, in both raw materials, is an important fraction and could be a sustainable alternative for the production of second generation ethanol, industrial enzymes, food/feed and fine chemicals such as lactic acid, succinic acid, etc. It can be easily converted into simple sugars by thermochemical processes and the resultant sugar solution after conditioning and detoxification, can be converted into the aforementioned products by biotechnological routes. Alterations in thermochemical processes such as implication of counter-current, plug-flow, percolation and shrinking-bed reactors could be helpful to maximize the sugars recovery with minimum inhibitors generation. There are several promising detoxification strategies available which remove the inhibitors from hydrolysates. The detoxified sugar solution can be converted into valuable products including second generation ethanol by appropriate microorganisms under batteries of fermentation. Laboratories based research progress has clearly showed that it is quite possible to convert hemicellulose into commercially significant products with desired yields and productivities. However, it is necessary to build a robust process to be employed at industrial scale. Bio-products derived from hemicellulose of SB/SS have shown potential to replace chemically synthesize products. Owing to this, bio-industrial companies offer numerous opportunities to develop unique functionality and marketing benefits from the products derived from hemicellulose of SB/SS creating long term sustainability and green environment.


The authors acknowledge the funding sources Fapesp, Capes and CNPq. Editors would like to thank EEL/USP for providing necessary facilities and basic infrastructure. We are grateful to BIOEN-FAPESP, CNPq and CAPES, Brazil for the financial assistance to our laboratory to carry out the research work on various aspects of lignocellulose biotechnology.


1 - Chandel AK, Silva SS, Carvalho W, Singh OV. Sugarcane Bagasse and Leaves: Foreseeable Biomass of Biofuel and Bio-products. Journal of Chemical Technology and Biotechnology 2012; 87 11–20.
2 - Companhia Nacional de Abastecimento. CONAB: Acompanhamento da Safra Brasileira de Cana-de-açúcar. Primeiro Levantamento-Abril/12. (accessed 28 May 2012).
3 - Pandey A, Soccol CR, Nigam P, Soccol VT. Biotechnological Potential of Agro-industrial Residues I: Sugarcane Bagasse. Bioresource Technology 2000; 74 69-80.
4 - Krishnan C, Sousa LC, Jin M, Chang L, Dale BE, Balan V. Alkali Based AFEX Pretreatment for the Conversion of Sugarcane Bagasse and Cane Leaf Residues to Ethanol. Biotechnology and Bioengineering 2010; 107 441–450.
5 - Soccol CR, Vandenberghe LPS, Medeiros ABP, Karp SG, Buckeridge MS, Ramos LP, Pitarelo AP, Ferreira-Leitão V, Gottschalk LMF, Ferrara MA, Bon EPS, Moraes LMP, Araujo JA, Torres FAG. Bioethanol from Lignocelluloses: Status and Perspectives in Brazil. Bioresource Technology 2010; 101 4820–4825.
6 - Dias MOS et al. Production of Bioethanol and Other Bio-based Materials from Sugarcane Bagasse: Integration to Conventional Bioethanol Production Process. Chemical Engineering Research and Design 2009; 87 1206–1216.
7 - Ojeda K, Avila O, Suarez J, Kafaro V. Evaluation of Technological Alternatives for Process Integration of Sugarcane Bagasse for Sustainable Biofuels Production – Part 1. Chemical Engineering Research and Design 2010; 89 270–279.
8 - Saha BC. Hemicellulosic Bioconversion. Journal of Industrial Microbial Biotechnology 2003; 30 279-291.
9 - Carvalheiro F, Duarte LC, Gírio FM Hemicellulose Biorefineries: A Review on Biomass Pretreatments. Journal of Scientific & Industrial Research 2008; 67 849-864.
10 - Girio FM, Fonseca C, Carvalheiro F, Duarte LC, Marques S, Bogel-Lukasik R. Hemicelluloses for Fuel Ethanol: A Review. Bioresource Technology 2010; 101 4775-4800.
11 - Kuhad RC, Gupta R, Khasa YP, Singh A, Zhang Y.-H. P Bioethanol Production from Pentose Sugars: Current Status and Future Prospects. Renewable and Sustainable Energy Review 2011; 15 4950-4962.
12 - Chandel AK, Singh OV. Weedy Lignocellulosic Feedstock and Microbial Metabolic Engineering: Advancing of Biofuel. Applied Microbial and Biotechnology, 2011; 89 1289-1303, 2011.
13 - Ensinas A, Modesto M, Nebra SA, Serra L. Reduction of irreversibility generation in sugar and ethanol production from sugarcane. Energy 2009; 34 680–688. DOI:10.1016/
14 - Neto MAT. Characterization of sugarcane trash and bagasse. In: Hassuani SJ, Leal MLRV, Macedo IC. Biomass Power Generation. Sugarcane Bagasse and Trash. Piracicaba: PNUD and CTC; 2005. p24.
15 - Singh P, Suman A, Tiwari P, Arya N, Gaur A, Shrivastava AK. Biological pretreatment of sugarcane trash for its conversion to fermentable sugars. World Journal of Microbiology and Biotechnology 2008; 24 667-673.
16 - Moriya RY. Use of microbial xylanases and laccases in the bleaching of organosolv pulps from sugarcane straw and study of the cellulosic derivatives obtained (Uso de xilanases e lacases de microrganismos no branqueamento de polpas organosolv de palha de cana-de-açúcar e estudo dos derivados celulósicos obtidos). PhD thesis. University of São Paulo, Engineering School of Lorena; 2007 [in Portuguese].
17 - Triana O, Leonard M, Saavedra F, Acan IC, Garcia OL, Abril A. Atlas of Sugarcane Bagasse. México: Geplacea and ICIDCA; 1990. p.139.
18 - Hatfield R, Fukushima RS. Can lignin be accurately measured? Crop Science 2005; 45 832-839.
19 - Paes LAD, Hassuani SJ. Potential trash and biomass of the sugarcane plantation, including trash recovery factors. In: Hassuani SJ, Leal MLRV, Macedo IC. Biomass Power Generation. Sugarcane Bagasse and Trash. Piracicaba: PNUD and CTC; 2005. p70.
20 - Filho JPR Characterization of sugarcane trash and bagasse. In: Hassuani SJ, Leal MLRV, Macedo IC. Biomass Power Generation. Sugarcane Bagasse and Trash. Piracicaba: PNUD and CTC; 2005. p78.
21 - Fengel D, Wegener G. Wood Chemistry, Ultrastructure, Reactions. Berlin: Walter de Gruyter; 1989, 613p.
22 - Pitarelo, A.P. Evaluation of susceptibility of sugarcane bagasse and straw on the bioconversion by steam-explosion and enzymatic hydrolysis (Avaliação da susceptibilidade do bagaço e da palha de cana-de-açúcar à bioconversão via pré-tratamento a vapor e hidrólise enzimática). Master thesis. Federal University of Paraná; 2007 [in Portuguese].
23 - Silva AS, Inoue H, Endo T, Yano S, Bon EPS. Milling pretreatment of sugarcane bagasse and straw for enzymatic hydrolysis and ethanol fermentation. Bioresource Technology 2010; 101 7402-7409.
24 - Canilha L, Santos VTO, Rocha GJM, Almeida e Silva JB, Giulietti M, Silva SS, Felipe MGA, Ferraz AL, Milagres AMF, Carvalho W. A study on the pretreatment of a sugarcane bagasse sample with dilute sulfuric acid. Journal of Industrial Microbiology and Biotechnology 2011; 38 1467-1475.
25 - Rocha GJM, Martin C, Soares IB, Souto Maior AM, Baudel HM, Abreu CAM. Dilute mixed-acid pretreatment of sugarcane bagasse for ethanol production. Biomass and Bioenergy 2011; 35 663-670.
26 - Singh A, Sharma P, Saran AK, Singh N, Bishnoi NR. Comparative study on ethanol production from pretreated sugarcane bagasse using immobilized Saccharomyces cerevisiae on various matrices. Renewable Energy 2012; 50 488-493.
27 - Martin C, Alriksson B, SJose A, Nilvebrant NO, Jonsson LJ. Dilute sulfuric acid pretreatment of agricultural and agro-industrial residues for ethanol production. Applied Biochemistry and Biotechnology 2007; 137-140 339-352. DOI 10.1007/s12010-007-9063-1
28 - Teixeira LC., Linden JC, Schroeder HA. Simultaneous saccharification and cofermentation of peracetic acid-pretreated biomass. Applied Biochemistry and Biotechnology 2000; 84-86 111-127. DOI 10.1385/ABAB:84-86:1-9:111
29 - Saad MBW, Oliveira LRM, Cândido RG, Quintana G, Rocha GJM, Gonçalves AR. Preliminary studies on fungal treatment of sugarcane straw for organosolv pulping. Enzyme and Microbial Technology 2008; 43 220-225.
30 - Luz SM, Gonçalves AR, Del’Arco Jr AP, Leão AL, Ferrão PMC, Rocha GJM. Thermal properties of polypropylene composites reinforced with different vegetable fibers. Advanced Materials Research 2010; 123-125 1199-1202.
31 - Rodrigues RCLB, Rocha GJM, Rodrigues Jr. DR, Filho HJI, Felipe MGA, Pessoa Jr. AP. Scale-up of diluted sulfuric acid hydrolysis for producing sugarcane bagasse hemicellulosic hydrolysate (SBHH). Bioresource Technology 2010; 101 1247-1253.
32 - Champagne P. Bioethanol from agricultural waste residues. Environmental Progress 2008; 27(1) 51-57
33 - Doherty WOS, Mousavioun P, Fellows CM. Value-adding to cellulosic ethanol: Lignin polymers. Industrial Crops and Products 2011; 33 259-276.
34 - Lavarack BP, Griffin GJ, Rodman D. The acid hydrolysis of sugarcane bagasse hemicellulose to produce xylose, arabinose, glucose and other products. Biomass and Bioenergy 2002; 23 367-380.
35 - Mosier N, Wyman C, Dale B, Elander R, Lee YY, Ladisch M. Features of promising technologies for treatment of lignocellulosic biomass. Bioresource Technology 2005; 96 673-686.
36 - Brodeur G, Yau E, Badal K, Collier J, Ramachandran KB, Ramakrishnan S. Chemical and physicochemical pretreatment of lignocellulosic biomass: A Review. Enzyme Research 2011;17p.
37 - Agbor VB, Cicek N, Sparling R, Berlin A, Levin D B. Biomass pretreatment: Fundamentals toward application. Biotechnology Advances 2011; 29 675-685.
38 - Sarkar N, Ghosh SK, Bannerjee S, Aikat K. Bioethanol production from agricultural wastes: An overview. Renewable Energy 2012; 37 19-27.
39 - Inoue H, Yano S, Endo T, Sakaki T, Sawayama S. Combining hot compressed water and ball milling pretreatments to improve the efficiency of the enzymatic hydrolysis of eucalyptus. Biotechnololy Biofuels 2008; 15 12p.
40 - Kumar P, Barret DM, Delwiche MJ, Stroeve P. Methods for pretreatment of lignocellulosic biomass for efficient hydrolysis and biofuel production. Industrial & Engineering Chemistry Research 2009. DOI: 10.1021/ie801542g
41 - Chornet E, Overend RP. Phenomenological kinetics and reaction engineering aspects of steam/aqueous treatments. In: ProcInt Workshop on Steam Explosion Techniques: Fundamentals and Industrial Applications. 1988. p.21-58.
42 - Kaar WE, Gutierrez CV, Kinoshita CM. Steam explosion of sugarcane bagasse as apretreatment for conversion to ethanol. Biomass and Bioenergy 1998; 14(3) 277- 287.
43 - Sun Y, Cheng J. Hydrolysis of lignocellulosic materials for ethanol production: A review. Bioresource Technology 2002; 83 1-11.
44 - Zheng Y, Pan Z, Zhang R. Overview of biomass pretreatment for cellulosic production. International Journal of Agricultural & Biological Engineering 2009; 2(3) 51-68.
45 - García-Cubero MT, Gonzalez-Benito G, Indacoechea I, Coca M, Bolado S. Effect of ozonolysis pretreatment on enzymatic digestibility of wheat and rye straw. Bioresource Technology 2009; 100 1608-1612.
46 - Vidal PF, Molinier J. Ozonolyzis of Lignin – Improvement of in vitro digestibility of poplar sawdust. Biomass 1988; 16 1-17.
47 - Vega A, Bao M, Lamas J. Application of factorial design to the modeling of organosolv delignification of Miscanthussinensis (Elephant grass) with phenol and dilute acid solutions. Bioresouresource Technology 1997; 61(1) 1-7.
48 - Taherzadeh MJ, Karimi K. Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: A review. International Journal of Molecular Sciences 2008; 9(9) 1621-1651.
49 - Singh A, Mishra P. Microbial Pentose Utilization. Current Applications in Biotechnology Progress in Industrial Microbiology; 1995 33.
50 - Aguilar R, Ramírez JA, Garrote G, Vásquez M. Kinetic study of the acid hydrolysis of sugarcane bagasse. Journal of Food Engineering 2002; 55 304-318.
51 - Magee RJ, Kosaric N. Bioconversion of Hemicelluloses. Advances in Biomechanical Engineering and Biotechnology 1985; 32 60-93.
52 - Winkelhausen E, Kuzmanova S. Microbial Conversion of D-xylose to Xylitol. Journal of Fermentation and Bioengineering 1998; 86(1) 1-14.
53 - Palmqvist E, Hahn-Hagerdal B. Fermentation of Lignocellulosic Hydrolysates. I: Inhibition and Detoxication Bioresource Technology 2000; 74 17-24.
54 - Rodrigues RCLB, Felipe MGA, Almeida e Silva JB, Vitolo M, Gómez PV. The influence of pH, temperature and hydrolysate concentration on the removal of volatile and nonvolatile compounds from sugarcane bagasse hemicellulosic hydrolysate treated with activated charcoal before or after vacuum evaporation. Brazilian Journal of Chemical Engineering 2001; 18(3) 299-311.
55 - Lima LHA, Felipe MGA, Vitolo M, Torres FAG. Effect of acetic acid present in bagasse hydrolysate on the activities of xylose reductase and xylitol dehydrogenase in Candida guilliermondii. Applied Microbiology and Biotechnology 2004; 65 734-738.
56 - Anish R, Rao M. Bioethanol from Lignocellulosic Biomass Part III Hydrolysis and Fermentation. Handbook of Plant-Based Biofuels, 2009; 159-173.
57 - Mussatto SI, Roberto IC. Alternatives for detoxification of diluted-acid lignocellulosic hydrolyzates for use in fermentative processes: A review. Bioresource Technology 2004; 93 1-10.
58 - Grzenia DL, Schell DJ, Wickramasighe SR. Membrane extraction for detoxification of biomass hydrolysates. Bioresource Technology 2012; 111 248-254.
59 - Chandel AK, Silva SS, Singh OV. Detoxification of Lignocellulosic Hydrolysates for Improved Bioethanol Production, Biofuel Production-Recent Developments and Prospects. InTech; 2011. ISBN: 978-953-307-478-8
60 - Canilha L, Almeida e Silva JB, Solenzal AIN. Eucalyptus hydrolysate detoxification with active charcoal adsorption or ion-exchange resins for xylitol production. Process Biochemistry 2004; 39 1909-1912.
61 - Carvalho W, Batista MA, Canilha L, Santos JC, Converti A, Silva SS. Sugarcane bagasse hydrolysis with phosphoric and sulfuric acids and hydrolysate detoxification for xylitol production. Journal of Chemical Technology and Biotechnology 2004; 79 1308–1312.
62 - Nilvebrant N, Reimann A, Larsson S, Jnsson LJ. Detoxification of Lignocelluloses Hydrolysates with ion-Exchange Resins. Applied Biochemistry and Biotechnology 2001; 91-93 35-49.
63 - Palmqvist E, Hahn-Hägerdal B. Fermentation of Lignocellulosic Hydrolysates II: Inhibitors and Mechanisms of Inhibition. Bioresource Technology 2000; 74 25-33.
64 - Mussatto SI, Roberto IC. Hydrolysate detoxification with activated charcoal for xylitol production by Candida guilliermondii. Biotechnology Letters 2001; 23 1681–1684.
65 - Canilha L, Carvalho W, Giulietti M, Felipe MGA, Almeida e Silva JB. Clarification of wheat straw-derived medium with ion-exchange resins for xylitol crystallization. Journal of Chemical Technology and Biotechnology 2008; 83 715-721.
66 - Wilson JJ, Deschatelets L, Nishikawa NK. Comparative fermentability of enzymatic and acid hydrolysates of steam-pretreated aspen wood hemicellulose by Pichia stipitis CBS 5776. Applied Microbiology and Biotechnology 1989; 31(5-6) 592-596.
67 - Cantarella M, Cantarella L, Gallifuoco A, Spera A, Alfani F. Comparison of different detoxification methods for steam-exploded poplar wood as a substrate for the bioproduction of ethanol in SHF and SSF. Process Biochemistry 2004; 39 1533–1542.
68 - Chaud LCS, Silva DDV, Felipe MGA. Evaluation of fermentative performance of Candida guilliermondii in sugarcane bagasse hemicellulosic hydrolysate detoxified with activated charcoal or vegetal polymer. In: Mendez-Villas A. Microbes in Applied Research: Current Advances and Challenges. World Scientific Publishing Co. Pte. Ltd.; 2012. ISBN: 978-981-4405-03-4
69 - Hou-Rui Z, Xiang-Xiang Q, Silva SS, Sarrouh BF, Ai-Hua C, Yu-Heng Z, Ke J, Qiu X. Novel Isolates for Biological Detoxification of Lignocellulosic Hydrolysate. Applied Biochemistry and Biotechnology 2009; 152 199-212.
70 - Yang B, Wyman CE. Pretreatment: the key to unlocking low-cost cellulosic ethanol. Biofuels, Bioproducts and Biorefining 2008; 2 26-40.
71 - Spiriodon I, Popa VI. Hemicelluloses: Structure and Properties. In: Dimitriu S. Polysaccharides: Structural Diversity and Functional Versatility. New York: Marcel Dekker; 2005. p1204.
72 - Peng F, Peng P, Xu F, Sun RC. Fractional purification and bioconversion of hemicelluloses. Biotechnology Advances 2012; 30 879-903.
73 - Cipriani TR, Mellinger CG, De Souza LM, Baggio CH, Freitas CS, Marques MC et al. A polysaccharide from a tea (infusion) of Maytenus ilicifolia leaves with anti-ulcer protective effects. Journal of Natural Products 2006; 69 1018–1021.
74 - Kardosova A, Malovikova A, Patoprsty V, Nosalova G, Matakova T. Structural characterization and antitussive activity of a glucuronoxylan from Mahonia aquifolium (Pursh) Carbohydrate Polymer 2002; 47 27–33.
75 - Kulicke WM, Lettau AI, Thielking H. Correlation between immunological activity, molar mass, and molecular structure of different (1→3)-β-D-glucans. Carbohydrate Research 1997; 297 135–143.
76 - Kitamura S, Hori T, Kurita K, Takeo K, Hara C, Itoh W et al. An antitumor, branched (1→3)-β-D-glucan from a water extract of fruiting bodies of Cryptoporus volvatus. Carbohydrate Research 1994; 263 111–121.
77 - Stone AL, Melton DJ, Lewis MS. Structure–function relations of heparin-mimetic sulfated xylan oligosaccharides: Inhibition of human immunodeficiency virus-1 infectivity in vitro. Glycoconjugate Journal 1998; 15 697–712.
78 - Watson K, Gooderham NJ, Davies DS, Edwards RJ. Interaction of the transactivating protein HIV-1 tat with sulphated polysaccharides. Biochemical Pharmacology 1999; 57 775–783.
79 - Bisaria VS, Ghose TK. Biodegradation of cellulosic materials: substrates, microorganisms, enzyme and products. Enzyme and Microbial Technology 1981: 3 90-104.
80 - Emodi A. Xylitol: Its Properties and Food Applications. Food Technology 1978; 28-32.
81 - Tovani Benzaquen, Segmentos, Cárneos e Derivados. (accessed 08 August 2012).
82 - Munday JC. News about glyconutrition, general nutrition, and related health issues. Xylose - An essential nutrient. Sweet Nutrition News 2003; (4).
83 - Zhang YHP, Ding SY, Mielenz JR et al. Fractionating recalcitrant lignocellulose at modest reaction conditions. Biotechnology and Bioengineering 2007: 97 214-223.
84 - Hyvönen L, Koivistoinen P, Voirol F. Food Technological Evaluation of Xylitol. Advances in Food Research 1982; 28 373-403.
85 - Knill CJ, Kennedy JF. Cellulosic Biomass-Derived Products. In: Dimitriu S. Polysaccharides: Structural Diversity and Functional Versatility. New York: Marcel Dekker; 2005. p1204.
86 - Kamm B, Gruber PR, Kamm M. The Biofine Process - Production of Levulinic Acid, Furfural, and Formic Acid from Lignocellulosic Feedstocks. In: Hayes DJ, Fitzpatrick S, Hayes MHB, Ross JRH. (ed.) Biorefineries- Industrial Processes and Products: Status Quo and Future Directions. DOI: 10.1002/9783527619849.ch7
87 - Wittcoff HA, Reuben BG, Plotkin JS. Industrial Organic Chemicals. New Jersey: John Wiley & Sons, Inc.; 2004. p662.
88 - Rosatella AA, Simeonov SP, Frade RFM, Afonso CAM. 5-hydroxymethylfurfural (HMF) as a building block platform: Biological properties, synthesis and synthetic applications. Green Chemistry 2011; 13 754-793.
89 - Lewkowski J. Synthesis, chemistry and applications of 5-hydroxymethylfurfural and its derivatives. Arquive for Organic Chemistry (Arkivoc) 2001; 17-54.
90 - Tokay BA. Biomass Chemicals. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA; 2005. p1-7. DOI 10.1002/14356007.a04 099
91 - Yun J, Jin F, Kishita A, Tohji K, Enomoto H. Formica acid production from carbohydrates biomass by hydrothermal reaction. Journal of Physics: Conference series 2010; 215 1-4.
92 - Aminoff C, Vanninen E, Doty TE. The occurrence, manufacture and properties of xylitol. In: Counsell JN (ed) Xylitol. London: Applied Science Publishers; 1978.
93 - BAR A. Xylitol, In: Nabors L0, Gelardi RC (ed.) Alternative sweetener. Nova York: Marcel Dekker, p349-379; 1991.
94 - Zarif L, Greiner J, Pace S, Riess JG. Synthesis of perfluoroalkylated xylitol ethers and esters: New surfactants for biomedical uses. Journal of Medicinal Chemistry 1990; 33(4) 1262-9.
95 - Castillo E, Pezzotti F, Navarro A, Lopez-Múnguia A. Lipase-catalyzed synthesis of xylitol monoesters: solvent engineering approach. Journal of Biotechnology 2003; 102 251-259.
96 - Makinen KK. Latest dental studies on xylitol and mechanism of action of xylitol in caries limitation. In: Greenby TH (ed.) Progress in sweeteners, London: Elsevier Applied Science; 1992, p 331-362.
97 - Aguiar CL, Oetterer M, Menezes TJB. Caracterização e aplicações do xilitol na indústria alimentícia. Bol. SBCTA 1999; 33(2) 184-93.
98 - Michel ACS. Produção biotecnológica de xilitol e etanol a partir de hidrolisado de casca de soja. Master dissertation. Universidade Federal do Rio Grande do Sul; 2007.
99 - Cruz JM, Dominguez JM, Domingues H, Parajo JC. Xylitol production from barley bran hydrolysates by continuous fermentation with Debaromyces hansenii. Biotechnology Letters 2000; 22 1895–1898.
100 - Izumori K, Tuzaki K. Production of xylitol from D-xylulose by Mycobacterius smegmatis. Journal of Fermentation Technology 1988; 66 33–36.
101 - Saha BC, Bothast RJ. Microbial production of xylitol. In: Saha BC., Woodward J. (eds.) Fuels and Chemicals from Biomass. Washington DC: American Chemical Society; 1997, p307–09.
102 - Felipe MGA. et al. Environmental parameters affecting xylitol production from sugarcane bagasse hemicellulosic hydrolysate by Candida guilliermondii. Journal of Industrial Microbiology and Biotechnology 1997; 18 251-254.
103 - Guindea R, Csutak O, Stoica I, Tanase AM, Vassu T. Production of xylitol by yeasts. Romanian Biotechnological Letters 2010; 15(3).
104 - Santos JC. Processo fermentativo de obtenção de xilitol a partir de hidrolisado de bagaço de cana-de-açúcar em reator de leito fluidizado: avaliação das condições operacionais. PhD thesis. Faculdade de Engenharia Química de Lorena; 2005
105 - Prakash G, Varma AJ, Prabhune A, Shouche Y, Rao M., Microbial production of xylitol from D-xylose and sugarcane bagasse hemicellulose using newly isolated thermotolerant yeast Debaryomyces hansenii. Bioresource Technology 2011; 102 3304–3308.
106 - Pereira AFF, Silva TC, Caldana ML, Machado MAAM, Buzalaf MAR. Revisão de Literatura: Utilização do xilitol para a prevenção de otite média aguda. International Archives of Otorhinolaryngology 2009; 3(1) 87-92.
107 - Kimberley T, Farquharson B. Sweet deal: Nova Green to produce healthy sugar substitute xylitol. Media Advisory: Nova Green Inc., 2012 (accessed June 2012).
108 - Prakasham RS, Sreenivasrao R, Hobbs PJ. Current trends in biotechnological production of xylitol and future prospects. Current Trends in Biotechnology and Pharmacy 2009; 3(1) 8-36.
109 - Rao RS, Jyothi P, Rao V. Biotechnological production of xylitol from hemicelulose materials. In: Kuhad RC, Singh A (ed) Lignocellulose biotechnology, Future Prospects; 2007.
110 - Cortez DV. Permeabilização de Células de Candida guilliermondii empregando Processos Químicos e Físicos e seu potencial uso como biocatalisadores na Síntese de Xilitol. PhD thesis. Escolha de Engenharia de Lorena EEL-USP São Paulo; 2010.
111 - Mussato SI, Dragone G, Guimarães PMR, Silva JPA, Cameiro LM, Roberto IC, Vicente A, Domingues L, Teixeira JA. Technological trends, global market and challenges of bio-ethanol production. Biotechnology Advances 2010; 28 817-830.
112 - Pacheco TF. Produção de Etanol: Primeira ou Segunda Geração?. Embrapa Agroenergia. ISSN 2177-4420, 2011. (acceessed 10 August 2012).
113 - Cerqueira Leite RC, Leal MRLV, Cortez LAB, Griffin WM, Scandiffio MIG. Can Brazil replace 5% of the 2025 gasoline world demand with ethanol?. Energy 2009; 34 655–661.
114 - Olsson L, Hanh-Hägerdal B. Fermentation of lignocellulosic hydrolysates.Enzymes and Microbiology Technology 1996; 18 312-331.
115 - Jeffries TW. Engineering yeasts for xylose metabolism. Current Opinion in Biotechnology 2006; 17 320-326.
116 - Agbogbo FK, Coward-Kelly G. Cellulosic ethanol production using the naturally occurring xylose-fermenting yeast, Pichia stipitis. Biotechnology letters 2008; 30 1515-1524.
117 - Delgenes JP, Moletta R, Navarro JM. Effects of lignocellulose degradation products on ethanol fermentations of glucose and xylose by Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, and Candida shehatae. Enzyme and Microbial Technology 1996; 19 220–225.
118 - Ha SJ, Galazkac JM, Kima SR, Choia JH, Yang X, Seoe JHN, Glassf L, Catec JHD, Jina YS. Engineered Saccharomyces cerevisiae capable of simultaneous cellobiose and xylose fermentation. Proceedings of the National Academy of Sciences (PNAS) 2011; 108 504–509.
119 - Canilha L, Carvalho W, Felipe MGA, Silva JBA, Giulietti M. Ethanol production from sugarcane bagasse hydrolysate using Pichia stipitis. Applied Biochemistry & Biotechnology 2010; 161 84–92.
120 - Hande A, Mahajan S, Prabhune A. Evaluation of ethanol production by a new isolate of yeast during fermentation in synthetic medium and sugarcane bagasse hemicellulosic hydrolysate. Annals of Microbiology 2012; DOI 10.1007/s13213-012-0445-4. Available from (accessed 10 August 2012).
121 - Chandel AK, Kapoor RK, Singh A, Kuhad RC. Detoxification of sugarcane bagasse hydrolysate improves ethanol production by Candida shehatae NCIM 3501. Bioresource Technology 2007; 98 1947-1950.
122 - Cheng KK, Cai BY, Zhang JA, Ling HZ, Zhou YJ, Ge JP, Xu JM. Sugarcane bagasse hemicellulose hydrolysate for ethanol production by acid recovery process, Biochemical Engineering Journal 2008; 38 105–109.
123 - Sindhu R, Kuttiraja M, Binod P, Janu KU, Sukumaran RK, Pandey A. Dilute acid pretreatment and enzymatic saccharification of sugarcane tops for bioethanol production. Bioresource Technology 2011; 102 10915-10921.
124 - Global Renewable Fuels Alliance. Global ethanol production to reach 88.7 billion liters in 2011. Available from (accessed 21 June 2012).
125 - Licht’s FO, F.O. Licht's World Ethanol & Biofuels Report. Available from (accessed 21 June 2012).
126 - Dürre, P. Fermentative butanol production. Annals of the New York Academy of Sciences 2008; 1125 353–362.
127 - Lee, S.Y., Park, J.H., Jang, S.H., Nielsen, L.K., Kim, J. and Jung, K.S. Fermentative Butanol Production by clostridia. Biotechnology and Bioengineering 2008; 101 209–228.
128 - Menon V, Prakash G, Rao M. Value Added Products from Hemicelluloses: Biotechnological Perspective. Global Journal Biochemistry 2010; 1 36–67.
129 - Atsumi S, Cann AF, Connor MR, Shen CR, Smith KM, Brynildsen MP, et al. Metabolic Engineering of Escherichia coli for 1-Butanol Production. Metabolic Engineering 2008; 10 305–311.
130 - Atsumi S, Hanai T, Liao JC. Non-Fermentative Pathways for Synthesis of Branched-Chain Higher Alcohols as Biofuels. Nature 2008; 451 86–89.
131 - Ezeji TC, Qureshi N, Karcher P, Blaschek HP. Butanol Production from Corn. In: S.D. Minter (ed.) Alcoholic fuels: fuels for today and tomorrow. New York: Taylor & Francis; 2006 p.99–122.
132 - Gapes JR. The Economics of Acetone-Butanol Fermentation: Theoretical and Market Considerations Journal of Molecular Microbiology and Biotechnology 2000; 2 27–32.
133 - Kosaric N, Magee RJ, Blaszczyk R. Redox Potential Measurement for Monitoring Glucose and Xylose Conversion by K. pneumonia. Chemical and Biochemical Engineering Quarterly 1992; 6 145–152.
134 - Tran AV, Chambers RP. The Dehydration of Fermentative 2,3-Butanediol into Methyl Ethyl Ketone. Biotechnology Bioengineering 1987; 29 343–351.
135 - Ji XJ, Nie ZK, Huang H, Ren LJ, Peng C, Ouyang PK. Elimination of Carbon Catabolite Repression in Klebsiella oxytoca for Efficient 2,3-Butanediol Production from Glucose-Xylose Mixtures. Applied Microbiology and Biotechnology 2011; 89 1119–1125.
136 - Willetts A. Butane 2,3-diol Production by Aeromonas hydrophila Grown on Starch. Biotechnology Letters 1984; 6 263–268.
137 - Groleau D, Laube VM, Martin SM. The Effect of Various Atmospheric Conditions on the 2,3-Butanediol Fermentation from Glucose by Bacillus polymyxa. Biotechnology Letters 1985; 7 53–58.
138 - Nakashimada Y, Marwoto B, Kashiwamura T, Kakizono T, Nishio N. Enhanced 2,3-Butanediol Production by Addition of Acetic Acid in Paenibacillus polymyxa. Journal of Bioscience and Bioengineering 2000; 90 661–664.
139 - Zhang L, Yang Y, Sun J, Shen Y, Wei D, Zhu J, Chu J. Microbial Production of 2,3-Butanediol by a Mutagenized Strain of Serratiamarcescens H30. Bioresource Technology 2010; 101(6) 1961-1967.
140 - Perego P, Converti A, Borghi AD, Canepa P. 2,3-Butanediol Production by Enterobacteraerogenes: Selection of the optimal Conditions and Application to Food Industry Residues. Bioprocess Engineering 2000; 23 613-620.
141 - Derraik JGB. The pollution of the marine environment by plastic debris: A review. Marine Pollution Bulletin 2002; 44 842-852.
142 - Reddy CSK, Ghai R, Rashmi, Kalia VC. Polyhydroxyalkanoates: An overview. Bioresource Technology 2003; 87 137-146.
143 - Thakor N, Trivedi U, Patel KC. Microbiological and biotechnological aspects of biodegradable plastics: Poly(hydroxyalkanoates). Indian Journal of Biotechnology 2006; 5 137-147.
144 - Castillo E, Pezzotti F, Navarro A, Lopez-Múnguia A. Lipase-catalyzed synthesis of xylitol monoesters: solvent engineering approach. Journal of Biotechnology 2003; 102 251-259.
145 - Ojumu TV, Yu J, Solomon BO. Production of Polyhydroxyalkanoates, a bacterial biodegradable polymer. African Journal of Biotechnology 2004; 3(1) 18-24.
146 - Suriyamongkol P, Weselake R, Narine S, Moloney M, Shah S. Biotechnological approaches for the production of polyhydroxyalkanoates in microorganisms and plants – A review. Biotechnology Advances 2007; 25 148-175.
147 - Lopes MSG, Rocha RCS, Zanotto SP, Gomez JGC, Silva LF. Screening of bacteria to produce polyhydroxyalkanoates from xylose. World Journal of Microbiology & Biotechnology 2009; 25 1751-1756.
148 - Koller M, Gasser I, Schmid F, Berg G. Linking ecology with economy: Insights into polyhydroxyalkanoate-producing microorganisms. Engineering in Life Sciences 2011; 11(3) 222-237.
149 - Mohanty AK, Misra M, Drzal LT, Selke SE, Harte BR, Hinrichsen G. Natural Fibers, Biopolymers, and Biocomposites: An Introduction. Natural Fibers, Biopolymers and Biocomposites, ISBN: 978-0849317415, Boca Raton: Taylor & Francis; 2005.
150 - Keenan TM, Nakas JP, Tanenbaum SW. Polyhydroxyalkanoate copolymers from forest biomass. Journal of Industrial Microbiology & Biotechnology 2006; 33 616-626.
151 - Yu J, Stahl H. Microbial utilization and biopolyester synthesis of bagasse hydrolysates. Bioresource Technology 2008; 99 8042-8048.
152 - Silva LF, Taciro MK, Ramos MEM, Carter JM, Pradella, JGC, Gomez JGC. Poly-3-hydroxybutyrate (P3HB) production by bacteria from xylose, glucose and sugarcane bagasse hydrolysate. Journal of Industrial Microbiology & Biotechnology 2004; 31 245-254.
153 - Mathews AJ, Tan H, Moore MJB, Bell G. A Conceptual Lignocellulosic ‘Feed+Fuel’ Biorefinery and its Application to the Linked Biofuel and Cattle Raising Industries in Brazil. Energy Policy. 2011; 39(9) 4932-4938.
154 - Kuhad RC, Singh A, Tripathi KK, Saxena RK, Eriksson KEL. Microorganisms as an Alternative Source of Protein. Topics in Food Science and Nutrition. 1997; 55 65–75.
155 - Lin Y, Tanaka S. Ethanol Fermentation from Biomass Resources: Current State and Prospects. Applied Microbiology Biotechnology 2006; 69 627-642.
156 - Zadrazil, F., Reiniger, P. Treatment of Lignocellulosics with White-rot Fungi. United Kingston: Elsevier; 1988, p117.
157 - Pessoa Jr A, Mancilha IM, Sato S. Cultivation of Candida tropicalis in sugarcane hemicellulosic hydrolysate for microbial protein production. Journal of Biotechnology 1996; 51(1) 83-88.