Efficient isopropanol-butanol (IB) fermentation of rice straw hydrolysate by a newly isolated Clostridium beijerinckii strain C-01

Abstract

In the present study, a Clostridium beijerinckii strain capable of producing Isopropanol-Butanol (IB) was isolated from gram grain. Batch fermentation of un-detoxified sulfuric acid pretreated rice straw (RS) hydrolysate (SARSH) with this strain resulted in the production of 6.6g L−1 acetone-free Isopropanol-Butanol (IB), of which butanol was 4.9 g L−1. Fermentation of hydrolysate obtained after ammonia pretreated enzyme hydrolysed RS resulted in the production of 8.5 g L−1 of acetone-free IB, giving a yield of 0.34 g g−1. IB production from fermentation of 30 g L−1 glucose and 30 g L−1 xylose was 10 and 8.6 g L−1, respectively, showing an equal and efficient utilization of both glucose and xylose. The total solvent yield from glucose and xylose was 0.36 and 0.32 g g−1 respectively. During fermentation mostly butanol (7.0 g L−1) and isopropanol (2.0 g L−1) were produced as biosolvents with negligible amounts of ethanol (0.1 g L−1). Since isopropanol can be used as a fuel additive, the mixture of isopropanol and butanol (IB) can be directly used as a biofuel.