酶法糖化玉米芯发酵生产乙醇的研究

Study on Enzymatic Hydrolysis of Corncob for Ethanol Production

研究了玉米芯的酶法水解及酶解液的乙醇发酵。采用里氏木霉ZU-02纤维素酶水解酸预处理后的玉米芯为原料,适宜的酶用量为20 FPIU(以每克底物计,下同),48 h后酶解得率为67.5%;添加黑曲霉ZU-07所产纤维二糖酶可有效解除纤维二糖累积引起的反馈抑制作用,当纤维二糖酶用量为6.5 CB IU时,48 h后酶解得率提高到83.9%。采用分批补料酶解工艺,使底物质量浓度提高到200 g/L,酶解60 h后还原糖质量浓度达到116.3 g/L,酶解得率为80.1%。利用一株耐高温酿酒酵母HTR-11在38℃下对酶解液进行乙醇发酵,质量浓度95.3 g/L的葡萄糖在18 h内发酵生成质量浓度为45.7 g/L的乙醇,其得率达到理论值的94%。

Enzymatic hydrolysis of corncob for ethanol fermentation from cellulosic hydrolysate was investigated. Corncob pretreated with dilute sulfuric acid was hydrolyzed by the cellulase from Trichoderma reesei ZU-02 at 50 ℃, pH value 4.8, and the hydrolysis yield was only 67.5 % due to poor cellobiase activity in T. reesei ZU-02 cellulase. Addition of cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield was improved to 83.9 % with cellobiase dosage of 6.5 CBIU/g substrate. A hydrolysis process using batch-wise feed was carried out to get a final substrate concentration of 200 g/L and the hydrolysis yield reached 80. 1 % after 60 h reaction. Furthermore, ethanol fermentation of cellulosic hydrolysate containing 95.3 g/L glucose was performed at 38 ℃ using a thermotolerant strain Saccharomyces cerevisiae HTR-11,45.7 g/L ethanol was obtained within 18 h and ethanol yield reached 94 % of the theoretical yield.