Identification and characterization of a novel 2,3‐butanediol dehydrogenase/acetoin reductase from Corynebacterium crenatum SYPA5‐5

Acetoin and 2,3‐butanediol are widely used in the chemical and pharmaceutical industries. The enzyme, 2,3‐butanediol dehydrogenase/acetoin reductase (2,3‐BDH/AR), plays a significant role in the microbial production of acetoin and 2,3‐butanediol by catalysing a reversible reaction between acetoin and 2,3‐butanediol. To date, a 2,3‐BDH has not been characterized from Corynebacterium crenatum. 2,3‐BDH was cloned from Coryne. crenatum SYPA5‐5 and expressed in Escherichia coli BL21. Sequence analysis suggested that the 2,3‐BDH from Coryne. crenatum SYPA5‐5 belongs to the short‐chain dehydrogenase/reductase superfamily. Its maximum specific activity was obtained at 35°C, however, it became very unstable when the temperature was above 35°C. Its optimal pH was 4·0 for reduction reaction and 10·0 for oxidation reaction. The 2,3‐BDH activity was increased to some extent by Ca²⁺, Mg²⁺, Zn²⁺ and Mn²⁺ ions. In particular, Ca²⁺ induced about 1·5‐fold increase. The value of kcₐₜ/Kₘ for diacetyl and acetoin are higher than for 2,3‐butanediol indicating that 2,3‐BDH can easily reduce diacetyl or acetoin to 2,3‐butanediol under lower pH conditions. The characteristics of 2,3‐BDH from Coryne. crenatum SYPA5‐5 will give guide to further studies for the production of acetoin and 2,3‐butanediol with engineered Coryne. crenatum SYPA5‐5. SIGNIFICANCE AND IMPACT OF THE STUDY: Acetoin and 2,3‐butanediol are commonly used as platform chemicals and widely used in pharmaceutical industries. 2,3‐butanediol dehydrogenase/acetoin reductase (2,3‐BDH/AR) plays a significant role in the microbial production of acetoin and 2,3‐butanediol. In this study, 2,3‐BDH was cloned from Corynebacterium crenatum SYPA5‐5, was expressed in Escherichia coli BL21 and characterized with respect to the optimal temperature, pH, substrate specificity and kinetics. The results will guide further studies in Coryne. crenatum SYPA5‐5 for the production of acetoin and 2,3‐butanediol.