Directional production of even carbon volatile fatty acids from peanut meal: effects of initial pH and hydraulic residence time

In this study, peanut meal was used as the substrate for the continuous production of even carbon volatile fatty acids (ECFA) through anaerobic fermentation. First, a continuous stirred reactor (CSTR) was started by adjusting the initial pH to acclimate the related bacteria, and then the hydraulic residence time (HRT) was optimized. The effects of different initial pH and HRT on the potential of ECFA production by peanut meal fermentation, the transformation and utilization of main organic compounds, and the composition and replacement of microbial community structure behind it were investigated. The results showed that ECFA was the dominant factor in the acid production of peanut meal fermentation, and alkaline pH and HRT = 6 d were the more favorable operating conditions for the hydrolysis and acidification of peanut meal. The average concentration of total volatile fatty acids (TVFAs) obtained was 15,249.50 mg/L, and the content of ECFA varied from 88.51% to 96.27%, with an average ratio of 92.55%. This operation condition drove the formation of microbial community structure, mainly including Prepotella, Tepididimicrobium, Anaerosalibacter, and Igatzschineria, which were favorable for ECFA production, reflecting the potential of using peanut meal for targeted production of ECFA.