PRODUCTION OF CYSTEINE OR CYSTINE FROM SERINE IN FERMENTATION MEDIUM

The present disclosure describes a method for producing cysteine and/or cystine comprising a) providing a fermentation medium comprising serine from of a genetically engineered host cell producing said serine; b) providing one or more sources of sulfur; c) providing one or more pyridoxal 5-phosphate (PLP)-dependent enzymes capable of converting serine into cysteine and/or cystine in the presence of the source of sulfur; d) contacting the serine in the fermentation medium with the pyridoxal 5-phosphate (PLP)- dependent enzyme in the presence of PLP and the source of sulfur under conditions allowing the serine to be converted into cysteine and/or cystine; and optionally e) recovering and/or isolating the cysteine and/or cystine.