One-pot fermentation of agricultural residues to produce butanol and hydrogen by Clostridium strain BOH3

Abstract

Solventogenic Clostridium strains usually do not ferment lignocellulosic biomass directly due to insufficient expression of hydrolyzing enzymes. In this study, we show that a solventogenic Clostridium strain BOH3 is able to produce both butanol and hydrogen when it ferments mixtures of agricultural residues and oil cakes. In particular, fermentation of mixed rice bran and sesame oil cake gives the highest butanol and hydrogen concentrations. In an optimized agro-residual medium (OAM) containing 94.5 g/l of rice bran and 36.7 g/l of sesame oil cake, BOH3 produces 13.50 ± 0.12 g/l of butanol and 4.41 ± 0.04 l/l of hydrogen after 7 days. Because BOH3 excretes hydrolyzing enzymes such as cellulase (0.52 ± 0.08 U/ml), xylanase (4.10 ± 0.05 U/ml) and amylase (2.05 ± 0.12 U/ml) during fermentation, BOH3 is able to perform fermentation and saccharification simultaneously when rice bran and sesame oil cakes are used as substrates. This is the first report showing that direct fermentation of agricultural residues by using solventogenic Clostridia is possible.