Biological formation of caproate and caprylate from acetate: fuel and chemical production from low grade biomass

Abstract

This research introduces an alternative mixed culture fermentation technology for anaerobic digestion to recover valuable products from low grade biomass. In this mixed culture fermentation, organic waste streams are converted to caproate and caprylate as precursors for biodiesel or chemicals. It was found that acetate, as the main intermediate of anaerobic digestion, can be elongated to medium chain fatty acids with six and eight carbon atoms. Mixed microbial communities were able to produce 8.17 g l À1 caproate and 0.32 g l À1 caprylate under methanogenesis-suppressed conditions in a stable batch reactor run. The highest production rate was 25.6 mM C caproate per day with a product yield of 0.6 mol C per mol C. This elongation process occurred with both ethanol and hydrogen as electron donors, demonstrating the flexibility of the process. Microbial characterization revealed that the microbial populations were stable and dominated by relatives of Clostridium kluyveri.

Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

“…Choi et al [20] reached a combined BA and HA titer of 32.0 g/L from sucrose in liquid-liquid extractive fermentation also by M. elsdenii. Bacterial co-cultures and mono-culture fermentations of C. kluyveri using acetate and ethanol as carbon sources produced HA titers of < 10 and 12.8 g/L, respectively [13,15,18,19] and Clostridium sp. BS-1 has been reported to produce up to 32 g/L of HA in 16 days from galactitol.…”

Production of Acetate from Carbon Dioxide in Bioelectrochemical Systems Based on Autotrophic Mixed Culture

“…To accomplish this objective, bioelectrochemical experiments were performed in the presence of 2-bromoethanesulfonic acid as an inhibitor of methanogenesis [23]. Setting electrode potentials is a useful approach to controlling the performance of BESs [6,12,26].…”

Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells

“…316 Mixed microbial communities produced 8.2 g/L hexanoate in a stable batch reactor run from equimolar ethanol and acetate. The highest hexanoate production rate was 0.15 g/(L h) with a yield of 0.65 g/g.…”