甘蔗渣是甘蔗工业的主要固体副产物,实现其高效生物转化的核心步骤是高效酶法水解。该研究通过酶制剂筛选与组合分析,发现β-葡萄糖苷酶(BgA)和外切葡聚糖酶(CbhC)与商品酶具有最优协同作用。将BgA和CbhC与商品酶复合,对甘蔗渣进行酶解并对复合酶酶解工艺进行研究和优化,在添加1 000 U/g商品酶的基础上,添加12 000 U/g BgA和0.175 U/g CbhC,50 ℃和pH 5.0下水解60 h的最优条件下,甘蔗渣中纤维素和半纤维素的水解率分别达到90.16%和95.65%。以此制得的甘蔗渣酶解液为碳源,进行乙醇发酵实验,乙醇产率达到30.30 g/L,转化率达到42.53%,木糖回收率为99.52%。该研究建立的酶法制糖工艺,可满足以甘蔗渣为原料生产生物乙醇的要求并可同步回收木糖。
Bagasse is the main solid by-product in sugarcane industry. Enzymatic saccharification of sugarcane bagasse is a core step for its biotransformation. Through screening of enzymes and combination analysis, minimal enzyme cocktails were developed for the saccharification of sugarcane bagasse. A β-glucosidase(BgA)and an exo-glucanase(CbhC)demonstrated the best synergistic effects with commercial enzyme cocktails. The highest hydrolysis rates of cellulose and hemicellulose reached 90.16% and 95.65%, respectively, under the optimal conditions of hydrolysis at 50℃ and pH 5.0 for 60 h, with 1 000 U/g commercial enzymes, 12 000 U/g BgA, and 0.175 U/g CbhC. The resultant enzymatic hydrolysates were used as the carbon source in ethanol fermentation by recombinant Escherichia coli. The yield of ethanol reached 30.30 g/L, and the conversion rate of glucose and recovery rate of xylose were 42.53% and 99.52%, respectively. The preliminary results obtained in this work are promising for ethanol production with a simultaneous xylose recovery.
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