Abstract
Fermentative production of L-serine using glycine as a precursor and Corynebacterium glycinophilum as a microbial producer was improved by decreasing the enzymatic degradation of L-serine. The cellular activity of L-serine dehydratase (SD) [EC 4.2.1.13], which was responsible for the L-serine degradation, was decreased in mutants that could not assimilate L-serine as a nitrogen, source or that required amino acids for their growth. Typical examples of the mutants were an L-leucine and L-isoleucine auxotroph (AJ-3414) which completely lacked SD and an L-leucine and L-methionine auxotroph (AJ-3413) whose SD activity was 32% of that of the parent. They accumulated 13.8 and 13.9mg/ml of L-serine, respectively, from 30mg/ml of glycine with a production yield of 46% as compared to the parental productivity of 15.3%.
