Fungal species producting keratinse.
Feathers are hard waste products, mainly composed of hard β-keratin, and are produced in large quantities in commercial poultry processing plants. Therefore, their industrial utilization is important economically as well as environmentally. Feathers degradation through keratinolytic microorganisms has been considered as an important method for efficient bioconversion, nutritional enhancement and eco-friendliness. The use of crude keratinase significantly increased the amino acid digestibility of raw feathers and commercial feather meal. This enzyme increased the digestibility of commercial feather meal and could replace as much as 7% of the dietary protein for growing chicks. However, feathers are currently utilized on a limited basis as a dietary protein supplement for animal feed because feather meal production is an expensive process, requiring significant amounts of energy. This review paper explains the nutritive value of feathers which makes suitable and inexpensive animal and poultry feed.
- feather meal
- animal feed
- protein hydrolysate
Rising livestock is a major industry, which produces animals that have multiple uses as meat, fibers and hides. It is important to feed the stock animals a proper balanced diet, to insure optimum growth and health. Feed Industries are seeking new way to cope with raw materials costs . Viable treated feather and hog hair meals have been found valuable sources of dietary protein for the growing chick . Recently, supplementation of poultry diets with enzyme mixtures, including protease and amylase has produced improvements in growth performance . Keratinase is an enzyme hydrolyses a broad range of protein substrate including casein, collagen, elastin and keratin . Scientist reported degradation of chicken feathers and other keratinous waste materials by fungi  and decomposed feathers were utilized as nitrogenous fertilizers due to their high value protein content [6, 7]. This feature of keratin protein can accomplish the shortage of meat raw materials and achieve desire of manufacturer to reduce production costs, and the availability of alternative sources of protein . Feather degradation by microbial action seems to be a reasonable substitute to obtain feather meal that would be nutritionally raised with essential amino-acids. This line of biodegradation of chicken feathers would convert the rigid feather waste to a readily digestible feather meal.
Keratin is hardened fiber plus matrix material which ultimately fills the cells of hair cortex. It thus consists of two main components; a fibrous protein which gives the α-keratin x-ray diffraction pattern (or the β-pattern when the polypeptide chains are extended as in feather keratin) and an amorphous protein which is termed γ-keratin . Only rare microorganisms like fungi, bacteria and actinomycetes are capable to break and utilize keratin because of their hard and tough nature. Humans and other vertebrates cannot digest this macromolecule, and if eaten, it simply gets accumulated within the variety of a lump that is still undigested. A large part of tiger scat and other carnivore dung contains scleroprotein (mainly hair) aside from bones and additional complex elements which are undigestible . Animal hair, hoofs, horns and wool contain β-keratin and bird’s feather contains α-keratin. Keratins are also present in epithelial covering which is rich in beta helical coil linked through cysteine bridges . The higher the percentage of sulfur, the higher is the stability of keratin towards solubilization . The keratin proteins are compound that are extremely resistant to action of physical, chemical and biological agents. Hair, horns, nails and cornified tissue are some naturally occurring forms of keratin [13, 14]. Keratin is a protein macromolecule with very high stability and low degradation rate.
Keratins are categorized into hard and soft keratins according to the sulfur content. Hard keratins have high content di-sulphide linking and are found in appendages. Soft keratins have low content of disulphide bond making skin and callus . Keratins belong to the super family of IF protein. Intermediate filament proteins are planned, prolonged α-helical conformation prone to form two-stranded coiled coils. The durability of keratins is a direct consequence of their complex architecture .
2.1 Chicken feathers
The main component of feather is keratin, a mechanically durable and chemically unreactive and insoluble protein, which render it difficult to be digested by most proteolytic enzymes. Keratin is resistant to enzymatic digestion by plant, animals and many known microbial proteases due to insoluble nature. Feathers having only 10% parts which is not keratin, rest 90% is resistant to degradation by common peptidases. This resistance is due to constituent amino acid composition and configuration that provide structural rigidity . Chicken feathers are made up of over 90% of keratin protein, small amounts of lipids and water. Feathers contain about 15% N on a dry weight basis and huge quantities are produced as industrial by product. However, they have not been used effectively as plant bio fertilizers since N mineralization are slow meet plant requirements . Feather waste, resulting in large quantities as by product of poultry farms processing, are pure keratin proteins.
3. Keratinases from microorganism
The keratinase producing micro-organisms have been discovered in several different biological groups, including fungi, bacteria and actinomycetes.
3.1 Bacterial strains
3.2 Actinomycetes strains
Thiosulfate production from cystine by keratinolytic prokaryote
3.3 Fungal strains
The thermophiles may be advantageous in comparison with mesophiles, because of their accelerated reaction processes and the accumulation of biomass and enzymes and diminished the risk of contamination in industrial activity. A large number of keratinases producing fungi were observed by . 234 fungal strains were isolated by baiting method used for feather degradation and keratinase producing ability. Maximum clearing zone was made by
|Fungal species||Aim of study||Author||References|
|Keratinase||Rajak et al.|||
|Keratinase||Kaul and Sumbali|||
|Keratinase production||Kaul and Sumbali|||
|Dehairing process||Anbu et al.|||
|Secretion of keratinase||Raju et al.|||
|Optimization of media composition||Kumar and Kushwaha|||
|Purification & Characterization||More et al.|||
|Purification of keratinase||Paul et al.|||
|Screening for keratinase||Kumar and Kushwaha|||
|Optimization in SSF Condition||Mini et al.|||
|Statistical optimization||Satyalakshmi et al.|||
4. Feathers as source of proteins and amino acids
An appealing alternating method to obtain amino acids and proteins is to use feathers that are relatively stable under natural conditions. Keratinophilic fungi used to hydrolyse keratin protein to obtain protein  and found maximum producer as
Conversion of feathers into feather meals by applying physical and chemical methods results in the loss of nutritionally essential amino acids such as methionine, lysine and tryptophan. Therefore, currently the poultry feathers are converted into feather meal, a digestible dietary protein, for animal feed using keratinases. The microbial production of L-lysine is an expanding branch of manufacturing biotechnology. There are many reports are available worldwide. Indian researcher  studied the discharge of cysteine in the culture medium.  recorded cysteine produced by
4.1 Animal feed
The upgradation of feather meal through microbial or catalyst treatment has been defined earlier. Feather meal fermented with
4.2 Feather meal as Chick feed
Meat and feather meal protein gave equally as good results as soybean meal protein when supplied 3% protein in practical-type corn-soybean meal rations .  observed growth of feather and composition in broiler chicken and found that that of threonine, isoleucine and valine increased with age while methionine content of feathers decreased with age.
Microbial keratinase substances improve keratin protein hydrolysis and increases nutritive value of feather meal. Microbial hydrolysed protein is rich in essential amino acid contents and other oligopeptides which are good and cheap for poultry feed. Supplementary learning outcome is desirable in an integrated sustainable approach to solve environmental issue of keratinous solid waste management and provide cheap and healthy feed.