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 30°C for its highest activity. The enzyme stability was decreased with increasing temperature and was completely vanished at 50°C. 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.