[Show abstract][Hide abstract] ABSTRACT: The fermentation of sucrose with Bacillus stearothermophilus ATCC 2027 afforded 2R,3R- and meso-2,3-butanediol together with R-acetoin following the bacterial catabolic pathway. This metabolic route was confirmed by the conversion of pyruvate to R-acetoin with the cell free extract of B. stearothermophilus. On the other hand the reduction of 3R-acetoin to 2R,3R- and meso-butanediol with the same cell free extract allowed at least the presence of two NADH-dependent reductases. Together with the S-stereospecific diacetyl reductase (BSDR), purified in a previous work, a new S-stereospecific acetoin reductase (S-ACR) was partially purified and a fraction containing R-stereospecific acetoin reductase (R-ACR) was obtained. On the other hand in B. stearothermophilus fermentation of sucrose the “butanediol cycle” is negligible because the acetylacetoin synthase, responsible of the first step of this cycle, is an inducible enzyme that needs low concentration of sugar and high concentration of acetoin to be expressed.
Full-text · Article · Apr 2011 · Journal of Molecular Catalysis B Enzymatic
[Show abstract][Hide abstract] ABSTRACT: Twelve strains of endophytic fungi, isolated from various plants (i.e. Eugenia hallii, Schinus molle, Crataegus monogyna, Juniperus communis and Sambucus nigra) sampled in Amazonian forest and in Italy, were screened for their reduction activity with a cocktail of ketones 1–4. The four most active strains [i.e. Phomopsis (FE86 and FE290), Pestalotia and Epicoccum] were chosen for the reduction of 5-hexen-2-one 1, acetophenone 2, cis-bicyclo[3.2.0]hept-2-en-6-one 3, 2-methylcyclohexanone 4, 6-methyl-5-hepten-2-one 5, 2-furyl methyl ketone 6, 1-indanone 7, and 2,4,4-trimethyl-2-cyclohexen-1-one 8 and in all cases the S-alcohols were obtained with variable yields and enantiomeric excesses depending on the strains.
Full-text · Article · Oct 2009 · Journal of Molecular Catalysis B Enzymatic
[Show abstract][Hide abstract] ABSTRACT: 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 synthase.