Key cellulase components synergizing with lactic acid bacteria to degrade alfalfa lignocellulose for improving lactic acid fermentation

Junfeng Li ¹ Linxiong Ma ² Wanyu Zhao ² Jingyu Wang ² Yanwen Li ² Yueying Xiong ² Yongchao He ² Xiaohui Chu ² Qinhua Liu ^2*

• ¹ Nanjing Agricultural University, Nanjing, Jiangsu Province, China
• ² Yunnan Agricultural University, Kunming, China

Cellulase converting alfalfa lignocellulose into lactic acid (LA) is valuable in low-temperature seasons for improving its fermentation quality, but which cellulase component synergized with lactic acid bacteria (LAB) to promote LA fermentation was unknown. This study aimed to clarify the key cellulase components that synergized with LAB in converting alfalfa lignocellulose into LA during ensiling from late fall to winter (3-20 ℃) over 140 days, using 7 combinations of cellulase component gene-engineered Lactococcus lactis (MG1363), cellulase (EN) and a combination of Lactobacillus plantarum and cellulase (LPEN) as parallel treatments, without treatment as a control (CON). EN degraded lignocellulose best. The pH value in the channel of converting sugars into LA was the key limiting factor for lignocellulose saccharification in LPEN. The optimal combination resulted in the fewest disaccharides (1.02 g/kg DM) and the highest conversion of water-soluble carbohydrates (WSC) to LA, up to 170%. It increased LA content to 80.0 g/kg DM maximally since cellobiohydrolase better cooperated with MG1363 to ferment lignocellulose into LA than endoglucanase and β-glucosidase. Strong LA production was approached by clarifying key cellulase components via cellulase component gene-engineered LAB.