Fusion protein including a fusion part and a protein of interest, the combination of the two proteins leading to the fusion protein being secreted into a supernatant of a bacterial host with the protein of interest being present in its correct three-dimensional structure. Nucleic acid including a sequence coding for a fusion protein, the sequence including: --F--As.sub.m--R.sub.n--Y--, where F is a nucleic acid sequence coding for an amino acid sequence which allows secretion of a protein encoded by Y into a fermentation medium, As is a chemical bond or a nucleic acid sequence comprising a codon, m is an integer from 0 10, R is a chemical bond or an arginine codon, n is 0 or 1, and Y is a nucleic acid sequence coding for a protein of interest. Processes therefor.