Isolation, characterization, and optimization of an aerobic butanol-producing bacterium from Singapore

We aimed to isolate aerobic butanol-producing microorganisms from environmental samples as potential platform strains for butanol production. Soil samples collected were subjected to a semi-high-throughput screening strategy. A microorganism capable of producing butanol in high concentrations under aerobic conditions was isolated and identified as Bacillus species by 16S rDNA analysis. The growth and butanol production under both aerobic and anaerobic conditions of the isolated Bacillus sp. 15, together with a different composition of by-products, suggest different metabolic networks from the obligate anaerobes Clostridia. At 1 L scale fermentation with 0.2 L/Min of ariflow, butanol titer reached up to 10.38 g/L in a batch culture. The fermentation process of the isolate also occurred in two phases and the acidic condition is critical for butanol production. The butanol concentration was further improved to 12.3 g/L with minimized by-products using a microaerobic condition. With the above-mentioned distinct features, the isolated Bacillus sp. 15 is a suitable platform strain for further process development and metabolic engineering for butanol production.