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 productio n of a fusion protein consisting of the pro-part of Staphylococcus hyicus l ipase and two synthetic human calcitonin (hCT) precursor repeats under the control of a xylose-inducible promotor from Staphylococcus xylosus. Using g lycerol as the energy source and pH-controlled addition of yeast extract re sulted 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 ti ter 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 precurso rs. Two hundred grams of the fusion protein was secreted by the recombinant S. carnosus on a 150-1 scale (scale-up factor of 50) with a minimum use of technical-grade yeast extract (40 mg fusion protein g(-1) yeast extract).