Enhanced hydrolysis and acidification of corn straw via liquid fraction of digestate: Environmental adaptability and microbial mechanisms

Anaerobic digestion (AD) of abandoned straws is an eco-friendly approach to realize its recycling. However, the low hydrolysis rate of lignocellulose poses a hindrance to achieving efficient AD. In this study, the enhanced hydrolysis and acidification of corn straw (CS) utilizing the liquid fraction of digestate (LFD) was investigated across varying solid-to-liquid inoculum ratio (SIR), pH levels, and temperature conditions. The succession patterns of the microbial community, driven by different parameters, were simultaneously identified. The findings revealed that the optimal yield of volatile fatty acids (VFAs) was observed under conditions with an SIR of 4, pH of 10, and a temperature of 45℃, predominantly dominated by acetic acid. And both pH and temperature were not conducive to VFAs accumulation in extreme environments. Comparatively, changes in pH had a greater impact on the acid production of the LFD-enhanced system and was also the primary environmental factor leading to differentiation in microbial community structure. Although Firmicutes was an absolutely dominant bacterium at the phylum level, the abundances of Caproiciproducens and Clostridum_sensu_stricto_1 at the genus level, mainly transforming complex organic substances into simpler metabolic byproducts, were greatly sensitive to the variations in SIR, pH, and temperature. This study could have practical implications for guiding improvements in large-scale AD systems with lignocellulosic straws.