细胞表面展示木聚糖酶对纤维素酶水解底物的协同促进作用

Synergistic effect of cell surface-displayed xylanase on cellulase during the hydrolysis of lignocellulosic substrates

为了解木质纤维素水解过程中木聚糖酶作为辅助酶对纤维素酶的协同促进作用，采用实验室保存的单展示3种纤维素酶（内切葡聚糖酶EGII、外切葡聚糖酶CBHII和β-葡糖苷酶BGLI）和2种木聚糖酶（β-D-1,4内切木聚糖酶XynII和β-D-1,4外切木聚糖酶XylA）的酿酒酵母功能菌群，以蒸汽爆破玉米秸秆为底物进行乙醇发酵实验（SSF）. 结果显示，以蒸汽爆破玉米秸秆为底物时，加入纤维素酶和木聚糖酶共发酵96 h的最高乙醇浓度达到0.695 g/L，乙醇产率为0.254 g/g，相当于理论值的49.8%，纤维素酶与木聚糖酶之间的协同因子（DS）最高达到1.16（始终大于1）. 本研究表明在细胞表面展示体系中适量添加木聚糖酶对纤维素酶水解底物具有较明显的促进作用，为直接以木质纤维素为原料制取纤维素乙醇提供了一定的可行性依据，可通过调节单展示酵母细胞在菌群间的动态比例实现对酶协同作用的优化调控. （图5 表3 参17）

The addition of xylanase has been found to effectively improve the performance of cellulases on Saccharomyces cerevisiae during the hydrolysis of lignocellulosic substrates. In this study, the effect of xylanase and xylosidase on cellulase during the hydrolysis of steam-exploded corn stalk was investigated. The HPLC analysis showed that with the addition of a mixture of cellulase and xylanase, the final ethanol concentration was 0.695 g/L 96-h after fermentation and the overall yield was 0.254 g of ethanol produced per gram of carbohydrate consumed, corresponding to 49.8% of theoretical value. The concentration of reducing sugar was 0.31 mg/mL, based on the 3,5-dinitrosalicylic acid method. Additionally, the degree of synergy was 1.16, and was always 〉 1. These results confirmed the synergistic effect of cellulase-xylanase, which was significantly higher than that of the treatments with a single enzyme. This highlights the synergistic effect of xylanase on cellulase during the hydrolysis of lignocellulosic substrates. It provides theoretical evidence, a feasible basis, and a certain reference value for the efficient production of lignocellulosic ethanol from lignocellulose directly. In the future, we can optimize the synergy between cellulase and xylanase by altering the proportion of the yeast strains.