Enhancing Alfalfa Hemicellulose Degradation by Anaerobic Bioprocessing with Engineered Xylanase-Secreting Pediococcus pentosaceus

To enhance hemicellulose utilization in alfalfa silage, Lactococcus lactis (NE) and Pediococcus pentosaceus (PE) expressing xylanase were engineered. The effects of recombinant LAB on hemicellulose utilization, fermentation characteristics, and microbiota diversity during alfalfa ensiling were investigated. The recombinant strains exhibited a 2.35-fold higher xylan degradation efficiency in comparison to the wild-type strains. Recombinant PE treatment significantly improved silage quality, with lactic acid (LA) production surging 149%, pH declining from 5.9 to 4.7 during the early stage (3 days), and hemicellulose degradation increased by 39.5% after 60 days of ensiling. Correlation analysis and KEGG pathway analysis confirmed that the relative abundance of Pediococcus affects the changes in the LA, hemicellulose, and carbohydrate catabolism. Compared to the control group, recombinant PE treatment increased in vitro dry matter digestibility (IVDMD, 20.2%), neutral detergent fiber digestibility (IVNDFD, 12.1%), and acid detergent fiber digestibility (IVADFD, 18.0%). Thus, the engineered strain secretes xylanase to enhance silage fermentation and fiber digestibility.