Microbial Transformation Of DL-Lactate To Pyruvate

The commercial demand for pyruvate is expanding since it has been widely sed in the industries of chemicals, drugs and agrochemicals. One high-throughput screening method was established based on the detection of pyruvate by the 2,4-dinitrophenylhydrazine （DNPH） method and high performance liquid chromatography （HPLC）. Five microorganisms were isolated with high activity of converting DL-lactate to pyruvate using the screening method. One of these strains numbered ZJB-07166 was identified as Serratia marcescens based on the morphology, physiological tests, ATB system （ID 32 E） and the 16S rDNA sequence. The NAD-independent lactate dehydrogenase was found in Serratia marcescens ZJB-07166.The culture and lactate dehydrogenase production conditions of Serratia marcescens ZJB-07166 were studied in details, and the enzyme activity increased evidently with the optimum production medium （DL-Lactate 1.0%, NH₄Cl 0.32%, K₂HPO₄ 0.1%, KH₂PO₄ 0.1%, MgSO₄·7H₂O 0.00032%, pH7.0）. And the results showed that Serratia marcescens ZJB-07166 lactate dehydrogenase was an inducible enzyme, and the enzyme production was correlated with the cell growth. During the preparation of biocatalyst, a prodigiosin-liked pigment was synthesized by Serratia marcescens ZJB-07166.Biotransformation process of DL-lactate by Serratia marcescens ZJB-07166 was studied. Pyruvate was degraded obviously with the addition of metal ions, and EDTA had an obvious stabilizing effect on pyruvate in biotransformation. The optimum biotransformation temperature and pH were 30℃and 6.0-8.0 respectively. The half-life of lactate dehydrogenase produced by Serratia marcescens ZJB-07166 was 84.5 h at 30℃. Higher substrate concentration than 60 mM exhibited inhibitive effect on enzyme activity, also the enzyme activity was inhibited by organic solvents, we added 60 mM lactate to the rotary shaker every 8 h, the highest accumulation of pyruvate achieved 210mM.