Fed-batch production of recombinant human calcitonin precursor fusion protein using Staphylococcus carnosus as an expression-secretion system

A pH-auxostatic fed-batch process was developed for the secretory production of a fusion protein consisting of the pro-part of Staphylococcus hyicus lipase and two synthetic human calcitonin (hCT) precursor repeats under the control of a xylose-inducible promotor from Staphylococcus xylosus. Using glycerol as the energy source and pH-controlled addition of yeast extract resulted in the production of 2000 mg l⁻¹ of the fusion protein (420 mg l⁻¹ of the recombinant hCT precursor) within 14 h, reaching 45 g l⁻¹ cell dry mass with Staphylococcus carnosus in a stirred-tank reactor. Product titer and space-time yield (30 mg calcitonin precursor l⁻¹ h⁻¹) were thus improved by a factor of 2, and 4.5, respectively, compared to Escherichia coli expression-secretion systems for the production of calcitonin precursors. Two hundred grams of the fusion protein was secreted by the recombinant S. carnosus on a 150-l scale (scale-up factor of 50) with a minimum use of technical-grade yeast extract (40 mg fusion protein g⁻¹ yeast extract). Received: 18 January 2000 / Received revision: 14 April 2000 / Accepted: 14 April 2000