Enhancement of lignocellulosic degradation in high-moisture alfalfa via anaerobic bioprocess of engineered Lactococcus lactis with the function of secreting cellulase

作者：Qinhua Liu, Junfeng Li, Jie Zhao, J.-P. Wu, Tao Shao · 发表于：Biotechnology for Biofuels · 年份：2019 · DOI：10.1186/s13068-019-1429-4 · 被引用次数：42 · 研究领域：Biofuel production and bioconversion、Microbial Metabolites in Food Biotechnology、Agricultural Productivity and Crop Improvement

Butyric fermentation and a substantial loss of dry matter (DM) often occur in alfalfa silage during the rainy season, which is not conducive to subsequent biofuel production. Currently, there have been negative effects on the combination of cellulases and lactic acid bacteria (LAB) on processing high-moisture alfalfa silage; however, transgenically engineered LAB strains that secrete cellulase have been proposed as an alternative approach to avoid the above problem. The objective of the present study was to construct engineered Lactococcus lactis strains with high-efficiency secretory-expressing cellulase genes from Trichoderma reesei and to investigate the effects of the combination of transgenically engineered L. lactis strains HT1 / pMG36e- usp 45- bgl 1, HT1 / pMG36e- usp 45- cbh 2, and HT1 / pMG36e- usp 45- egl 3 (HT2) on fermentation quality, structural carbohydrate degradability and nonstructural carbohydrate fermentation kinetics of high-moisture alfalfa silage treated without additive as a negative control (Control), or/and with cellulase (EN), wild-type L. lactis subsp. lactis MG1363 (HT1) and the combination of HT1 and EN (HT1 + EN) as positive additive controls. Engineered L. lactis strains were successfully constructed and efficiently secreted endoglucanase (1118 mU/mL), cellobiohydrolase (222 mU/mL), and β-glucosidase (131 mU/mL) and had high filter paper activity (236 mU/mL). Ensiling experiments verified that HT2 obtained the highest fermentation quality score...