Abstract:[Objective] NAD-dependent D-lactate dehydrogenase (D-LDH) catalyzed the conversion of pyruvate to D-lactic acid. However, the weakness of thermostability of D-LDHs reported to date hindered the recombinant strain construction for high-temperature fermentation process. Finding a novel thermostable D-LDH would lay the foundation for constructing the efficient D-lactate producer under high-temperature fermentation conditions and thus will reduce the operation cost of producing D-lactic acid. [Methods] D-LDH was cloned from Lactobacillus jensenii strain and then expressed in Escherichia coli to determine its optimal reaction temperature, optimal reaction pH, kinetic parameter, thermostability and thermal inactivation, which is compared with the mesophilic D-LDH from Lactobacillus plantarum ssp. plantarum. [Results] D-LDH from Lactobacillus jensenii strain had higher optimal reaction temperature (45 °C), better thermostability and 3 times higher catalytic activity (kcat/Km) than those of D-LDH from Lactobacillus plantarum ssp. plantarum (optimal reaction temperature was just 30 °C). [Conclusion] D-LDH from Lactobacillus jensenii strain had better thermostability and higher catalytic activity, which is useful component for industrial applications.
