John Rojas

By John Rojas

Part of the book: Cellulose

By John Rojas, Mauricio Bedoya and Yhors Ciro

The goal of this chapter is to review the most recent trends to produce cellulose nanoparticles and nanocomposites with biomedical applications. These particles could be named as bacterial cellulose, cellulose nanofibers, and cellulose nanocrystals. The production of these nanoparticles with diameters below 100 nm is challenging because of the strong agglomeration tendency which occur upon drying aqueous cellulose suspensions or during the compounding process with hydrophobic polymers. Typically, the physical and mechanical properties of these nanoparticles depend on the source of cellulose and the extraction process employed. Cellulose nanoparticles are obtained by mechanical, chemical, or enzymatic process treatments to open the structure of the cellulose source and facilitate accessibility to its microstructure. Usually, a combination of these processes makes the extraction more efficient.

Part of the book: Cellulose

By Julián Quintero, Ana Naranajo, Gelmy Ciro and John Rojas

Plant-derived proteins are remarkable macromolecules of scientific interest because they represent an alternative to the animal-derived proteins and petroleum-derived polymers. Many food proteins especially those derived from animal sources could act as antigens in humans. For instance, milk proteins extracted from cows may cause food intolerance during infancy. Further, soybean, peanuts, tree nuts, fish, crustacean shellfish and egg proteins may act as antigens in 90% of children. Since the GI tract is permeable to intact antigens the oral intake of these proteins may generate gastrointestinal (50–80%), cutaneous (20-40%) and respiratory symptoms (4–25%). Most of these allergens are water-soluble glycoproteins that are resistant to acids and enzymes. Usually, these proteins have a small molecular weight (10,000–60,000 kDa), water solubility, glycosylation residues, and a relative resistance to heat and digestion. Allergenicity is less frequent in vegetable proteins due to their less flexible and non-compact structure. Allergenicity is also related to the resistance to proteolysis, post-translational glycosylation, presence of epitopes, and enzymatic proteolysis. Moreover, proteins serve as a coating material if structural modifications in the protein, either by physical, chemical or enzymatic mechanisms are conducted. As a result, their allergenicity is reduced, and their functional properties are enhanced.

Part of the book: Allergen

By John Rojas, Julian Qunitero, Yhors Ciro, Alfredo Moreno, Javier Silva-Agredo and Ricardo A. Torres-Palma

The global annual production of shrimp is nearly 4 million metric tons generating almost half of this weight in waste. This study assessed the crop production of legumes fertilized with shrimp exoskeletons obtained by microwaves under greenhouse conditions. Plants were grown under the following fertilization regimes: (i) untreated shrimp waste, (ii) shrimp waste pellets, (iii) shrimp-based pellets having a hydrolysis degree of 42%, (iv) untreated cellulose pellets, (v) untreated soil, (vi) untreated cotton substrate, and (vii) two commercial fertilizers (CF1 and CF2). CF1 and CF2 showed the largest electric conductivity and ionic exchange capability, whereas the fertilizing pellets showed the lowest values. However, pH, densification and conductivity of soil were not affected by fertilization. Shrimp waste showed a high content of C, N, O, Ca and P mainly derived from chitin, proteins and minerals. All fertilizers showed typical type II isotherms, but the untreated soil and CF2 per se exhibited the largest water uptake. The soil microbiota increased during the growing cycle and then decreased as the reproductive phase started. Further, soil planted with Phaseolus vulgaris showed a larger microbial population than Pisum sativum. The best plant growth was achieved when treated with CF2, whereas the raw shrimp waste caused a beneficial plant growth and crop yield mainly in Phaseolus vulgaris.

Part of the book: Food Preservation and Waste Exploitation