Patent ID: 9689009
Date: 2017-06-27
CPC Classifications: C12N,C12P,C12Y

Claim:
1. A method for producing cysteine or a derivative thereof, comprising: (a) culturing a recombinant microorganism in which the activity of an endogenous phosphoserine phosphatase (SerB) and a phosphonate transporter (PhnCDE; phnC (ATP-binding component of phosphonate transport, EG 10713)-phnD (periplasmic binding protein component of Pn transporter, EG 10714)-phnE (integral membrane component of the alkylphosphonate ABC transporter, EG 11283)) is reduced, and the activity of a phosphoglycerate dehydrogenase (SerA) is enhanced, to produce O-phosphoserine (OPS); wherein the level of endogenous SerB or PhnCDE activity is reduced by deletion of the endogenous SerB or PhnCDE gene wherein the level of SerA activity is increased by increasing copy number of the SerA gene or changing an endogenous promoter into a strong promoter, wherein the phosphoserine phosphatase comprises the amino acid sequence of SEQ ID NO: 1 or SEQ ID NO:2 and wherein the SerA having increased activity comprises the amino acid sequence selected from the group consisting of SEQ ID NOs: 3, 5, 6, and 7; and (b) reacting the OPS of step (a) with a sulfide in presence of O-phosphoserine sulfhydrylase (OPSS) or a microorganism expressing OPSS, to produce cysteine or derivatives thereof, wherein the OPSS comprises the amino acid sequence selected from the group consisting of SEQ ID NOs: 9, 10 and 12; wherein the recombinant microorganism has been further modified to (i) enhance the activity of a nucleotide transhydrogenase (PntAB), wherein the level of nucleotide transhydrogenase activity is enhanced by increasing the copy number of a gene encoding the nucleotide transhydrogenase or changing an endogenous promoter into a strong promoter; and/or (ii) enhance the activity of at least one enzyme selected from the group consisting of o-acetylserine/cysteine efflux permease (YfiK), homoserine/homoserine lactone efflux protein (RhtB), and threonine/homoserine efflux protein (RhtC), wherein the level of enzyme activity is enhanced by increasing the copy number of a gene encoding the enzyme or changing an endogenous promoter into a strong promoter.