Wang-Jin Lim

Production of l-Methionine-enriched cells of a mutant derived from a methylotrophic yeast, Candida boidinii

l-Methionine-enriched cells production of an ethionine-resistant mutant of Candida boidinii no. 2201 was greatly improved by the control of pH and by feeding of methanol and other medium components during cultivation in a jar fermentor. Under the optimal conditions, 38.5 g (as dry weight)_of cells abd 282 mg of pool methionine (intracellular pool of free l-methionine) per l of culture broth were obtained after 11 d of cultivation. The culture conditions for production of l-methionine-enriched cells in continuous culture were investigated. With limited methanol in continuous cultivation, pool methionine productivity reached a maximum value of 1.14 mg·l−1·h−1 at a dilution rate of 0.05·h−1. During methanol-limited growth in continuous cultivation, the pool methionine content of the mutant was about 20–35% higher than that in batch cultivation.

Biochemical Characterization of an L-Methionine-Enriched Mutant of a Methylotrophic Yeast, Candida boidinii

Abstract The effects of an ethionine-resistant mutation in a methylotrophic yeast, Candida boidinii , were studied. In mutant strain E500-78 (ethionine-resistant), SAM synthetase activity was low and was only slightly repressed by l -methionine. Formyltetrahydrofolate synthetase and serine hydroxymethyltransferase were involved in synthesis of the methyl group of l -methionine. The activities of the methyl group transferring enzymes and homocysteine transmethylation were repressed by l -methionine in the wild type strain, but not in the mutant. The activities of the methyl group transferring enzymes were markedly stimulated when the mutant was grown in methanol medium.