Method for producing n-acetyl-d-glucosamine and/or d-glucosamine salt by microbial fermentation

A method for producing N-Acetyl-D-Glucosamine and/or D-Glucosamine salt by microbial fermentation, comprising:

• A) culturing a microorganism in a fermentation medium to produce said N-Acetyl-D-Glucosamine and/or D-Glucosamine salt, wherein said microorganism is transformed with at least one recombinant nucleic acid molecule comprising a nucleic acid sequence encoding N-acetvl-D-aminomannose-6-phosphate epimerase (NanE);
• said nucleic acid sequence encoding N-acetvl-D-aminomannose-6-phosphate epimerase (NanE) comprises at least one genetic modification that increases the activity of N-acetyl-D-aminomannose-6-phosphate epimerase (NanE) relative to a N-acetyl-D-aminomannose-6-phosphate epimerase without said genetic modification;
• wherein said N-acetyl-D-aminomannose-6-phosphate epimerase comprises an amino acid sequence having at least 95% sequence identity to the amino acid sequence of SEQ ID NO:
• 17 and the cysteine at position 133 of the amino acid sequence of SEQ ID NO:
• 17 is substituted with arginine and the tyrosine at position 187 of the amino acid sequence of SEQ ID NO:
• 17 is substituted with histidine ;
• and
• B) collecting N-Acetyl-D-Glucosamine and/or D-Glucosamine salt produced in the culturing step A).