Production of 2,3-butanediol by Bacillus stearothermophilus: fermentation and metabolic pathway

The fermentation of different sugars by Bacillus stearothermophilus ATCC 2027 to obtain 2,3-butanediol is described. Fermentation tests in shake flasks show the complete conversion of sucrose to butanediol (91% yield) and acetoin (3-hydroxy-2-butanone) using a starting sugar concentration of 30 g/L. A similar result is obtained with sugar cane molasses, whereas glucose and fructose afford lower yields. Other disaccharides and monosaccharides are also tested without appreciable results. B. stearothermophilus forms a mixture of 2R,3R-butanediol and the meso isomer derived both from reduction of R-acetoin and from the butanediol cycle as demonstrated by the presence of acetoin reductase and acetylacetoin synthas