Adding Ethanol to the Batch and Continuous Transplantation Co-Culture of Maize Straw Fermented by Rumen Fluid for the Production of Caproic Acid

In this study, to enhance the concentration of caproic acid generated from maize straw fermentation and clarify the structures of bacterial and fungal communities within the successively domesticated rumen microbial fermentation system, maize straw was used as the substrate. In a continuous subculture system, the impacts of ethanol addition on pH and gas production were explored, with a focus on the caproic acid yield in the final (eighth generation) generation and alterations in bacterial and fungal communities. Results demonstrated that ethanol could boost the caproic acid concentration in maize straw fermentation by rumen fluid to 1,492 mg/L. Analysis of the microbial community structure indicated that unidentified_Clostridiales, Shuttleworthia, and Syntrophococcus were crucial in ethanol-driven caproic acid production. These findings are highly significant for the high - value utilization of maize straw waste to produce caproic acid via the carboxylic acid platform using rumen microorganisms in industrial processing.