High-Rate Production of Short-Chain Fatty Acids from Methane in a Mixed-Culture Membrane Biofilm Reactor

The bioconversion of methane to liquid chemicals has attracted much attention. However, the production rate reported to date has been far lower than what is required for economical viability. This is partly due to the low solubility of methane, the low mass transfer rate, and low microbial activities. This study demonstrates a production rate of close to 10 g of short-chain fatty acids (SCFAs) per liter per day with a mixed-culture biofilm growing in a membrane biofilm reactor (MBfR). Hollow fiber membranes were used both to deliver a high flux of methane and to provide a surface on which slow-growing microorganisms could form biofilms with intensified activities. The rate achieved is nearly 2 orders of magnitude higher than the highest SCFA production rate reported to date and is close to the rates required for practical applications (∼12-120 g L^-1 day^-1). The consortium in the biofilm was dominated by methanogens Methanosarcina and Methanobacterium and acid-producing bacteria Sporolactobacillus and Propionispora, suggesting likely roles of these organisms in the bioconversion of methane into SCFAs. This work shows a methane-based MBfR represents a promising technology for achieving high-rate production of chemicals from methane. © 2018 American Chemical Society.