Recombinant peptide production using a cross-linkable solubility tag

A process to obtain a peptide of interest from a fusion peptide comprising:

• a) providing a population of fusion peptides comprising the general structure:
• IBT-CS-POI
• or
• POI-CS-IBT
• wherein;
• i) IBT is an inclusion body tag that does not include a cysteine residue;
• ii) CS is a cleavage site;
• and
• iii) POI is a peptide of interest comprising an effective number of cysteine residues;
• b) cleaving the population of fusion peptides at said cleavage site whereby the inclusion body tag is no longer linked to the peptide of interest and whereby a mixture of peptide molecules is produced comprising a plurality of inclusion body tags and a plurality of peptides of interest;
• c) subjecting the mixture of peptide molecules of step (b) to oxidizing conditions whereby the peptides of interest are cross-linked;
• and
• d) recovering the peptide of interest.