Discovery and Engineering of a Bacterial (+)‐Pulegone Reductase for Efficient (−)‐Menthol Biosynthesis

Abstract

AbstractThe biosynthesis of valuable plant‐derived monoterpene (−)‐menthol from readily available feedstocks (e. g., (−)‐limonene) is of great significance because of the high market demand for this product. However, biotransforming (+)‐pulegone into (−)‐menthone, the (−)‐menthol precursor, through (+)‐pulegone reductase (PGR) catalysis is inefficient because of the poor protein expression or catalytic efficiency (kcat/Km) of plant origin PGRs. In this study, a novel bacterial PGR from Pseudomonas resinovorans (PrPGR) was identified, and the most successful variant, PrPGRM2‐1 (A50 V/G53 W), was obtained, showing respective 20‐fold and 204‐fold improvements in specific activity and catalytic efficiency. PrPGRM2‐1 was employed to bioreduce (+)‐pulegone, resulting in 4.4‐fold and 35‐fold enhancements in (−)‐menthone titers compared with the bioreductions catalyzed by wild‐type (WT) PrPGR and MpPGR, respectively. Furthermore, a whole‐cell biocatalyst containing PrPGRM2‐1, MpMMR, and BstFDH was constructed and achieved the highest (−)‐menthol titer reported to date without externally supplemented NADPH/NADP+. Overall, this study details an efficient PGR with high catalytic efficiency that possesses great potential for (−)‐menthol biosynthesis.