Application of cellulase-polyamidoamine dendrimer-modified silica for microwave-assisted chitosan enzymolysis

Enhancing nonspecific enzymatic hydrolysis of chitin to oligosaccharides pretreated by acid and green solvents under simultaneous microwave-radiation

It is hard to degrade untreated highly crystalline chitin. In this study, two solvents pretreatment chitin (acid swollen chitin (AC), super fine chitin (FC)) and microwave-heating method were used to enhance nonspecific enzymatic hydrolysis (lysozyme and pepsin), which obviously improved the enzymolysis rates by at least 1.31 times. Characterizations of chitin substrates (M_v, SEM, XRD) showed that calcium solvent pretreatment (obtained FC) was milder but effective than phosphoric acid pretreatment (obtained AC). The highest yield of chitin oligosaccharides (37.58 mg/g) were obtained after hydrolyzing AC under five-hour simultaneous microwave radiation by pepsin, among them, the content of N-acetylglucosamine was 13.76 mg/g. While, more chitin oligosaccharides with DP (degree of polymerization) 3-4 and lower DA (degree of acetylation) were obtained when using lysozyme than pepsin. Significantly, the conversion rate of chitin to oligosaccharides went best only when microwave and enzymes acting together (simultaneous strategy), which were at least 35.59% higher than separately pretreatment enzymes and substrates by microwave. The damages of microwave radiation on lysozyme and chitin substrates were revealed, and the operating principle of the whole enzyme reaction system heated by microwave was preliminatively explored.

Hydrolysis of trichosanthin (TCS) catalyzed by imidazolium-based ionic liquids in heating and microwave-assisted modes

Two modes of TCS hydrolysis based on ILs were compared and a higher degree of hydrolysis can be obtained compared to common catalysts.

Optimization and Characterization of Chitosan Enzymolysis by Pepsin

Pepsin was used to effectively degrade chitosan in order to make it more useful in biotechnological applications. The optimal conditions of enzymolysis were investigated on the basis of the response surface methodology (RSM). The structure of the degraded product was characterized by degree of depolymerization (DD), viscosity, molecular weight, FTIR, UV-VIS, SEM and polydispersity index analyses. The mechanism of chitosan degradation was correlated with cleavage of the glycosidic bond, whereby the chain of chitosan macromolecules was broken into smaller units, resulting in decreasing viscosity. The enzymolysis by pepsin was therefore a potentially applicable technique for the production of low molecular chitosan. Additionally, the substrate degradation kinetics of chitosan were also studied over a range of initial chitosan concentrations (3.0~18.0 g/L) in order to study the characteristics of chitosan degradation. The dependence of the rate of chitosan degradation on the concentration of the chitosan can be described by Haldane’s model. In this model, the initial chitosan concentration above which the pepsin undergoes inhibition is inferred theoretically to be about 10.5 g/L.