Characteristics of D-lactate Dehydrogenase from the High Potential D-lactic Acid Producer Leuconostoc pseudomesenteroides TC49 Isolated from Thailand

Abstract

D-lactate dehydrogenase obtained from Leuconostoc pseudomesenteroides TC49, a D-lactic acid producing bacterium isolated from a Tithonia diversifolia flower in Thailand, was studied its properties for use in D-lactic acid production. Successful protocols of protein precipitation, dialysis, ultrafiltration and chromatography were used for D-LDH purification. The purified D-LDH with its N-terminal amino acid sequence as MKIFAYGIRE displayed the molecular weight of approximate 40.6 kDa with preferred pH of 8.5 and temperature of 30C for its highest activity. The enzyme stability was decreased with increasing temperature and was completely vanished at 50C. The kcat, Km and kcat/ Km of the purified enzyme in the pyruvate reduction were 180 s-1, 0.5 mM and 360 mM-1 s-1 while the values in the D-lactate oxidation were 117 s-1, 69.6 mM and 1.681 mM-1s-1, respectively. AgNO3 and ZnCl2 slightly inhibited the purified enzyme.