Production of L-malic acid via biocatalysis employing wild-type and respiratory-deficient yeasts.

The yeast Saccharomyces cerevisiae has been used to efficiently produce L-malic acid from fumaric acid. Fumarase is responsible for the reversible conversion of fumaric and L-malic acids in the TCA cycle. To investigate the function of mitochondrial and cytoplasmic fumarase isoenzymes in L-malic acid bioconversion, a wild-type strain and a cytoplasmic respiratory-deficient mutant devoid of functional mitochondria were employed. The mutant strain, which only contained the cytoplasmic fumarase, was still functional in fumaric acid to L-malic acid bioconversion However, its specific conversion rate was much lower (0.20 g/g.h) than that of the wild-type strain (0.55 g/g.h).