An NADPH-dependent Lactobacillus composti short-chain dehydrogenase/reductase: characterization and application to (R)-1-phenylethanol synthesis.

A new anti-Prelog short-chain dehydrogenase/reductase (SDR) encoding gene lcsdr was cloned from Lactobacillus composti DSM 18527, and heterologously expressed in Escherichia coli. LcSDR is nicotinamide adenine dinucleotide phosphate (NADPH)-dependent and has a molecular weight of approximately 30 kDa. The optimal pH and temperature were 6.5 and 30 °C, respectively. The maximal reaction rate Vmax was 133.9 U mg-1; the Michaelis-Menten constant K m of LcSDR were 0.345 mM for acetophenone (1a), and 0.085 mM for NADPH. Through introducing an EsGDH-catalyzed NADPH regeneration system, a biocatalytic process for (R)-1-phenylethanol ((R)-1b) was developed with outstanding time-space yield. Under the optimized conditions, 50 g l-1 1a was converted to (R)-1b in 2 h with a yield of 93.8%, enantiomeric excess of product (e.e.p) above 99% and space-time yield of 562.8 g l-1 d-1.