Highly efficient synthesis of(R)-1,3-butanediol via anti-Prelog reduction of 4-hydroxy-2-butanone with absolute stereoselectivity by a newly isolated Pichia kudriavzevii

(R)-1,3-butanediol is an important pharmaceutical intermediate, and the synthesis of(R)-1,3-butanediol using green biological methods has recently been of interest for industrial application. Here, a novel strain QC-1 that efficiently transforms 4-hydroxy-2-butanone to(R)-1,3-butanediol was isolated from soil samples. Based on morphological, physiological, and biochemical tests and 5.8 S-internal transcribed spacer sequencing, the strain was identified as Pichia kudriavzevii QC-1. The reaction conditions were optimized to 35 ℃, pH 8.0, rotation speed 200 rpm, and 6:5 mass ratio of glucose to 4-hydroxy-2-butanone. Evaluation of the effects of 4-hydroxy-2-butanone concentrations on yield and cell survival rate showed that 85.60 g·L^-1 product accumulated, with an enantiomeric excess of more than 99%, when 30 g·L^-14-hydroxy-2-butanone was added at 0, 10, and 30 h in a 3-L bioreactor. Thus, strain QC-1 showed excellent catalytic activity and stereoselectivity for the synthesis of(R)-1,3-butanediol from 4-hydroxy-2-butanone.

Enzymatic cascade systems for D-amino acid synthesis:progress and perspectives

D-amino acids,different from the ubiquitous L-amino acids,are recognized as the“unnatural”amino acids.The applications of D-amino acids have drawn increasing interest from researchers in recent years,and D-amino acids are widely used in various industries,including for food products,pharmaceuticals,and agricultural chemicals.Inspired by the prevalent appli-cations,many synthetic methods for D-amino acids have been developed,which are mainly divided into chemical synthetic methods and biosynthetic methods.Chemical synthesis of D-amino acids has a variety of disadvantages such as multiple reaction steps,low yields,low reaction rates,and difficulties in product extraction.Thus,biosynthetic methods utilizing enzymes are attracting increasing attention because they are more energy-saving and environmentally friendly compared to traditional chemical synthesis.Among all enzymatic methods,multi-enzymatic cascade catalytic methods have significant advantages,such as lower costs,no need for intermediate separation,and higher catalytic efficiency,which is ascribed to the spatial proximity of biocatalysts.In this review,advances in multi-enzyme cascade catalytic systems as well as chemo-enzymatic approaches to synthesize D-amino acids are discussed.