Study On The Microbial Production Of (R)-1,3-butanediol

(R)-1,3-butanediol((R)-1,3-BDO)is an important chiral synthon for synthesis of various optical active compounds such as azetidione derivatives,key intermediate of penem and carbapenem antibiotics,pheromones,fragrances and insecticides.More and more attention was focused on efficient production of(R)-1,3-BDO.With high stereselectivity,high activity and environmental benign,interests in chiral biocatalyst aroused.The asymmetric oxidation or reduction of prochiral derivatives by oxidoreductase has become an important alternative for optical chiral alcohols synthesis.In this paper,the microbial synthesis of(R)-1,3-BDO from 4-hydroxy-2-butanone(4H2B)was explored.Firstly we established a gas chromatography analysis of 4H2B and(R)-1,3-BDO.Then strain ZJB-09162,a yeast with high stereselectivity and activity toward 4H2B was isolated from soil samples.Based on morphology,physiological characteristics and 18S rDNA analysis,ZJB-09162 was identified as Candida krusei.To improve the enzyme production of ZJB-09162,the medium components and cultivation conditions of ZJB-09162 were optimized.The results showed that the optimal medium components is as follows(g/L):glucose 50.0,yeast extract 50.0,(NH4)2HP04 2.5,KH2PO4 2.5,NaCl 1.0.The optimal cultivation conditions were initial pH 6.0,loading capacity 12%,inoculum size 4%.Under the optimal conditions,the biomass of ZJB-09162 reached 15.2 g DCW/L and the carbonyl reductase activity reached 120U/L.Simultaneously,the asymmetric reduction of 4H2B by resting cells of ZJB-09162 were optimized.The data showed that the optimal reaction temperature and cosubstrate glucose concentration were 35?and 8%(w/v),respectively.The optimal buffer was pH 8.5 Tris-HCl.After 36 hour-reaction with 400 mM 4H2B under the optimal conditions,the e.e.value and yield of(R)-1,3-BDO reached 99%and 210 mM,respectively.