纤维素酶系碱性条件下的选择性失活及应用
详细信息Selective denaturation of major enzymatic components in cellulase system by alkali treatment and its application
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摘要: 里氏木霉产纤维素酶系中的内切葡聚糖酶（CMCase）、纤维二糖水解酶（CBH）和β-葡萄糖苷酶三大酶类在碱性处理条件下会发生快速、选择性失活。在pH9.00和（25±1）℃的条件下静置处理纤维素酶液30min,CMCase和CBH酶组分主要发生可逆变性失活,而β-葡萄糖苷酶发生不可逆变性失活,它们的残余酶活力分别为58.8%、56.6%和5.7%,相对比例可达到10.3和9.9。通过碱性处理能够得到低β-葡萄糖苷酶活力的纤维素酶制剂,可以显著提高其定向酶水解纤维素制备纤维低聚糖的生产性能,并生成以纤维二糖为主包括少量纤维三糖的纤维低聚糖。以0.1%（v/v）碱处理纤维素酶定向水解10g/L纸浆24h,纤维低聚糖的酶解得率为6.73%,占总糖类的78.2%,比天然酶反应体系提高53.6%。Abstract: In the crude cellulase system of Trihcoderma reesei, three main enzyme groups involving endo-glucanase (CMCase) , cellobiohydrolase (CBH) and β-Glucosidase were rapidly and selectively denatured in the alkali circumstance. CMCase and CBH were inclined to reversible denaturation, different from the irreversible denaturation of β-Glucosidase as the crude cellulase was incubated statically in the alkali solution at pH9. 00 and (25±1) ℃ for 30min. The residual enzyme activity value of three enzyme groups were respectively remained 58. 8% of CMCase, 56. 6% of CBH and 5. 7% of β-Glucosidase, thus the relative ratio between CMCase or CBH and β-Glucosidase reached 10. 3 or 9. 9. Alkali treatment improved greatly, the cellulase selectivity and produced the glucosidase-poor cellulase to hydrolyze selectively cellulose into cellooligosaccharides containing mainly cellobiose and little cellotriose. The product yield of cellooligosaccharide could reach 6. 73% when 10g/L paper powder solution was hydrolyzed at the enzyme loading of 0. 1% (v/v) alkali treated cellulase for 24h. The oligosaccharides content accounted for 78. 2% of the total degraded saccharides which increased by 53. 6%, compared with the enzymatic hydrolysate with crude cellulase.
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