纤维素酶水解壳聚糖的特性研究

The hydrolysis mechanism of chitosan by cellulase

利用粘度法、还原端基法及TLC法,探讨了温度、pH、反应时间、底物的脱乙酰度和金属离子等对纤维素酶水解壳聚糖的影响。结果表明,纤维素酶能有效降解壳聚糖,其作用的最适温度为60℃,最适pH为5.2,酶水解反应米氏常数为Km=10mg/mL;Mn2+、Mg2+、Ca2+对该酶有较强的激活作用,Ag+、Cu2+、Hg+、葡萄糖等是该酶的抑制剂。该酶稳定性较强,在pH3～7的范围内均很稳定,60℃作用1h相对残余酶活为60.8%。其最适作用的底物为脱乙酰度(DD)90%的壳聚糖,根据水解产物分析判断其以内切酶为主,既能水解GlcN-GlcN键,又能水解GlcNAc-GlcN键。

The effects of reaction temperature, pH, reaction time, substrate concentration, and deacetylation degree （DD） on the hydrolysis of chitosan by cellulase were investigated by measuring changes in viscosity and reducing sugar in this paper. The results showed that the optimal conditions for depolymerization of chitosan with cellulase were at 60℃ and pH 5.2. The data revealed that the km value was 10mg/mL. The enzyme activity was increased by the addition of Na^｜, Mg^2＋, Ca^2＋, Mn^2＋ while it was strongly inhibited by the addition of Ag^＋, Cu^2＋, Hg^＋ and glucose, the relative activity still retained 60.8% at 60℃ for lh., The best substrate was colloid chitosan with 90% DD. It was suggested that this enzyme is an endo-type chitosanase and cleaved both GlcNAc-GlcN and GlcNAc-GlcN linkage based on the analysis the hydrolysate.