Pyruvate producing biocatalyst with constitutive NAD-independent lactate dehydrogenases

Abstract

Production of pyruvate from lactate through biocatalysis is a valuable process for its simple composition of reaction system and convenience of recovery. Biocatalyst with lactate-induced NAD-independent lactate dehydrogenases (iLDHs) can effectively catalyze lactate into pyruvate. To reduce the cost of biocatalyst preparation caused by indispensable lactate addition, the mutants with constitutive iLDH of Pseudomonas sp. XP-M2 were screened. Mutant XP-LM exhibited high iLDHs activities in minimal salt medium with cheap substrate glucose as the carbon source. The biocatalyst (8.2 g dry cell weight l −1) containing 169.8 U l −1 l-iLDH was prepared with 20 g 1 −1 glucose. The cost-effective biocatalyst prepared from the mutant XP-LM could efficiently catalyze lactate into pyruvate with high yield (0.961 mol mol −1). Based on the different thermostability of d-iLDH and l-iLDH in the biocatalyst, whole cells of the strain might also have the potential in production of pyruvate and d-lactate from racemic lactate.