Erythritol production in cyanobacteria

Abstract

The present invention relates to a process for producing erythritol and to a cyanobacterial cell for the production of erythritol.

1 . A cyanobacterial cell capable of expressing, preferably expressing, at least one functional enzyme selected from the group of enzymes consisting of a phosphatase and a reductase; preferably of an erythrose-phosphatase, an erythritol-phosphatase, and an erythrose reductase; more preferably of an erythrose-4-phosphate reductase and an erythritol-4-phosphate phosphatase, or of an erythrose-4-phosphate phosphatase and an erythrose reductase. 
     
     
         2 . A cyanobacterial cell according to  claim 1 , expressing at least an erythrose-4-phosphate reductase and an erythritol-4-phosphate phosphatase, or an erythrose-4-phosphate phosphatase and an erythrose reductase. 
     
     
         3 . A cyanobacterial cell according to  claim 1 , wherein the at least one functional enzyme is a heterologous enzyme. 
     
     
         4 . A cyanobacterial cell according to  claim 1 , wherein the at least one functional enzyme is selected from the group consisting of an erythrose-4-phosphate phosphatase from  Thermotoga maritima, Escherichia coli  or  Synechocystis  PCC6803 and an erythrose-4-phosphate reductase from  Saccharomyces cerevisiae, Candida magnolia, Trichoderma reesei, Aspergillus niger  or  Penicillium chrysogenum.    
     
     
         5 . A cyanobacterial cell according to  claim 1 , wherein the at least one functional enzyme comprises or consists of a polypeptide that has an amino acid sequence with at least 30% sequence identity with a sequence selected from the group consisting of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10, SEQ ID NO: 12, SEQ ID NO: 14 and SEQ ID NO: 16. 
     
     
         6 . A cyanobacterial cell according to  claim 1 , wherein the at least one functional enzyme is encoded by a polynucleotide that has a nucleic acid sequence with at least 30% sequence identity with a sequence selected from the group consisting of SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13 and SEQ ID NO: 15. 
     
     
         7 . A cyanobacterial cell according to  claim 1 , wherein the cyanobacterial cell is a  Synechocystis , preferably a  Synechocystis  PCC 6803. 
     
     
         8 . A cyanobacterial cell according to  claim 1 , wherein a polynucleotide encoding the at least one functional enzyme is under control of a regulatory system which responds to a change in the concentration of a nutrient when culturing said cyanobacterial cell. 
     
     
         9 . A process for producing erythritol comprising culturing a cyanobacterial cell according to  claim 1  under conditions conducive to the production of erythritol and, optionally, isolating and/or purifying the erythritol from the culture broth. 
     
     
         10 . A process according to  claim 9 , wherein the culture conditions comprise feeding carbon dioxide to the culture and/or subjecting the culture to light.