Engineered Bacillus subtilis 168 produces l-malate by heterologous biosynthesis pathway construction and lactate dehydrogenase deletion

In the present work, Bacillus subtilis was engineered to produce l-malate. Initially, the study revealed that the slight fumarase activity under anaerobic conditions is extremely favourable for l-malate one-step fermentation accumulation. Subsequently, an efficient heterologous biosynthesis pathway formed by Escherichia coli phosphoenolpyruvate carboxylase and Saccharomyces cerevisiae malate dehydrogenase was introduced into B. subtilis, which led to 6.04 +/- A 0.19 mM l-malate production. Finally, the l-malate production was increased 1.5-fold to 9.18 +/- A 0.22 mM by the deletion of lactate dehydrogenase. Under two-stage fermentation conditions, the engineered B. subtilis produced up to 15.65 +/- A 0.13 mM l-malate, which was 86.3 % higher than that under anaerobic fermentation conditions. Though the l-malate production by the recombinant was low, this is the first attempt to produce l-malate in engineered B. subtilis and paves the way for further improving l-malate production in B. subtilis.