High potential lignocellulose-degrading microbial seed exploration from various biogas plants for methane production

Abstract

Converting lignocellulosic materials into renewable energy through anaerobic digestion (AD) often has low degradation efficiency and thus needs improvement. Inoculum seeds from biogas plants fed with cow manure (CM), pig manure (PM), Napier grass (NG), and goat manure (GM) were explored for high-potential lignocellulose-degrading inocula based on the biochemical methane potential. Overall, CM, PM, and GM seeds could degrade lignocellulose. However, PM inoculum exhibited the highest CH4 production rate from cellulose powder, xylan, and Napier grass degradation by 46.32, 49.61, and 18.56 NmL/gVSadded·d, indicating the shortest lag phase but lagged behind GM and CM for alkali lignin. Microbial community analysis revealed lignocellulose-degrading microorganisms in the inocula. A high relative abundance of cellulose-degrading bacteria, such as Anaerolineaceae, Romboutsia, Bacteroidetes vadinHA17, and Clostridium sensu stricto 1, was detected. Anaerobic lignin-degrading bacteria were found in CM, PM, and GM inocula. Moreover, Bathyarchaeia from the archaeal group involved in lignocellulose degradation was found in CM and GM inocula. Keystone methanogens for methanogenesis were also detected in all inocula. PM inoculum possesses a promising inoculum seed for shortening the start-up period of the lignocellulose-degrading reactor with high AD performance and stability as it provides a short lag time and a high rate of methanogenesis.