High production of acetoin from glycerol by Bacillus subtilis 35

Acetoin is a high-value volatile compound widely applied in the chemical, food, and pharmaceutical industries. Despite the promising use of waste glycerol as a substrate in several microbial syntheses, acetoin production by natural microorganisms from glycerol as a sole carbon source has never been reported. The present study investigates the innate ability of Bacillus subtilis 35 (DSM 113,620) to convert glycerol into acetoin and 2,3-butanediol. The fermentation was directed towards acetoin production by medium selection and process parameter optimization using response surface design methodology. Thus, the fed batch conducted under optimized conditions received 77.9 g/L acetoin with a productivity of 0.85 g/L h and a yield of 0.36 g/g. The obtained acetoin concentration is the highest from glycerol reported to date, comparable to the highest values gained from glucose. Transcription analysis of the gene cluster glpPFKD showed that all four genes responsible for the utilization of glycerol were expressed. This natural ability of the strain, along with its non-pathogenic nature, defines B. subtilis 35 as a very promising candidate for acetoin production from glycerol on an industrial scale.