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.
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机译：胃蛋白酶用于有效降解壳聚糖，以使其在生物技术应用中更有用。在响应面法（RSM）的基础上研究了酶解的最佳条件。降解产物的结构通过解聚度（DD），粘度，分子量，FTIR，UV-VIS，SEM和多分散指数分析来表征。壳聚糖降解的机理与糖苷键的断裂有关，从而使壳聚糖大分子链断裂成较小的单元，导致粘度降低。因此，胃蛋白酶的酶解是生产低分子壳聚糖的潜在适用技术。另外，还研究了在一定范围的初始壳聚糖浓度（3.0〜18.0 g / L）下壳聚糖的底物降解动力学，以研究壳聚糖的降解特性。壳聚糖降解速率对壳聚糖浓度的依赖性可以通过Haldane模型来描述。在该模型中，理论上推断胃蛋白酶受到抑制的初始壳聚糖浓度约为10.5 g / L。
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