The efficient production of human epidermal growth factor by Bacillus brevis

A system has been developed for the efficient production of heterologous proteins using Bacillus brevis as a host that secretes large amounts of cell wall protein into the medium. The promoter region and signal peptide-encoding region of the cell wall protein gene were used to construct an expression-secretion vector. Bacterial proteins such as amylases can be produced in large amounts by this system (1 g/l or more), but mammalian proteins such as human alpha-amylase are produced at a low level (one or two orders of magnitude less than for bacterial proteins). The highly efficient secretion of human epidermal growth factor (h-EGF, more than 1 g/l) was obtained with B. brevis HPD31 as the host and plasmid pHY481, derived from B. brevis 481, as the vector. Recombinant hEGF was purified easily from the culture supernatant by two steps. Purified hEGF had the identical NH2-terminal amino acid sequence and COOH-terminal amino acid sequence with those of the authentic hEGF, and it was fully active in biological assays. This recombinant hEGF has been shown to be successful for biological wool harvesting (CSIRO, Australia). These results, in combination with previous results, indicate that foreign proteins of diverse origins can be produced efficiently as functional proteins in B. brevis.