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Applied Biochemistry and Biotechnology, Vol.178, No.3, 604-617, 2016
Cloning, Expression, and Characterization of budC Gene Encoding meso-2,3-Butanediol Dehydrogenase from Bacillus licheniformis
The budC gene encoding a meso-2,3-butanediol dehydrogenase (BlBDH) from Bacillus licheniformis was cloned and overexpressed in Escherichia coli BL21(DE3). Sequence analysis reveals that this BlBDH belongs to short-chain dehydrogenase/reductase (SDR) superfamily. In the presence of NADH, BlBDH catalyzes the reduction of diacetyl to (3S)-acetoin (97.3 % ee), and further to (2S,3S)-2,3-butanediol (97.3 % ee and 96.5 % de). Similar to other meso-2,3-BDHs, it shows oxidative activity to racemic 2,3-butanediol whereas no activity toward racemic acetoin in the presence of NAD(+). For diacetyl reduction and 2,3-butanediol oxidation, the pH optimum of BlBDH is 5.0 and 10.0, respectively. Unusually, it shows relatively high activity over a wide pH range from 5.0 to 8.0 for racemic acetoin reduction. BlBDH shows lower K (m) and higher catalytic efficiency toward racemic acetoin (K (m) = 0.47 mM, k (cat) /K (m) = 432 s(-1)center dot mM(-1)) when compared with 2,3-butanediol (K (m) = 7.25 mM, k (cat) /K (m) = 81.5 s(-1)center dot mM(-1)), indicating its physiological role in favor of reducing racemic acetoin into 2,3-butanediol. The enzymatic characterization of BlBDH provides evidence for the directed engineering of B. licheniformis for producing enantiopure 2,3-butanediol.