Production of 2-keto-l-gulonic acid

A recombinant microorganism comprising an integrated polynucleotide fragment containing a polynucleotide encoding a protein having L-sorbose dehydrogenase (SDH) activity, said polynucleotide being selected from the group consisting of:

• (a) polynucleotides encoding a polypeptide comprising the amino acid sequence according to SEQ ID NO:2;
• (b) polynucleotides comprising the nucleotide sequence according to SEQ ID NO:1;
• (c) polynucleotides comprising a nucleotide sequence obtainable by nucleic acid amplification such as polymerase chain reaction, using genomic DNA from a microorganism as a template and a primer set according to SEQ ID NO:3 and SEQ ID NO:4;
• (d) polynucleotides comprising a nucleotide sequence encoding a fragment or derivative of a polypeptide encoded by a polynucleotide of any of (a) to (c) wherein in said derivative one or more amino acid residues are conservatively substituted compared to said polypeptide, and said fragment or derivative has the activity of a SDH polypeptide;
• (e) polynucleotides the complementary strand of which hybridizes under stringent conditions to a polynucleotide as defined in any one of (a) to (d) and which encode a SDH polypeptide;
• (f) polynucleotides which are at least 70%, such as 85, 90 or 95% homologous to a polynucleotide as defined in any one of (a) to (d) and which encode a SDH polypeptide;
• or the complementary strand of such a polynucleotide and wherein said polynucleotide being integrated into the genome of the recombinant microorganism and wherein the integration site is selected from the group consisting of L-sorbose reductase gene locus, 2-keto-L-gulonic acid reductase gene locus, glucose dehydrogenase gene locus and cytochrome bd oxidase gene locus.