Characterization and genome analysis of a butanol–isopropanol-producing Clostridium beijerinckii strain BGS1

BACKGROUND: One of the main challenges of acetone–butanol–ethanol fermentation is to reduce acetone production with high butanol yield. Converting acetone into isopropanol is an alternative pathway to reduce fermentation by-products in the fermentation broth. Here, we aimed to cultivate a wild-type Clostridium strain with high isopropanol and butanol production and reveal its genome information. RESULTS: Clostridium beijerinckii strain BGS1 was found to be capable of producing 10.21 g/L butanol and 3.41 g/L isopropanol, higher than previously known wild-type isopropanol–butanol-producing Clostridium species. Moreover, culture BGS1 exhibited a broad carbon spectrum utilizing diverse sugars such as arabinose, xylose, galactose, cellobiose, and sucrose, with 9.61 g/L butanol and 2.57 g/L isopropanol generated from 60 g/L sucrose and less amount from other sugars. Based on genome analysis, protein-based sequence of strain BGS1 was closer to C. beijerinckii NCIMB 8052, reaching 90.82% similarity, while compared to C. beijerinckii DSM 6423, the similarity was 89.53%. In addition, a unique secondary alcohol dehydrogenase (sAdhE) was revealed in the genome of strain BGS1, which distinguished it from other Clostridium species. Average nucleotide identity analysis identified strain BGS1 belonging to C. beijerinckii. The transcription profile and enzymatic activity of sAdhE proved its function of converting acetone into isopropanol. CONCLUSIONS: Clostridium beijerinckii strain BGS1 is a potential candidate for industrial isopropanol and butanol production. Its genome provides unique information for genetic engineering of isopropanol–butanol-producing microorganisms.