Evaluation of parallel operated small-scale bubble columns for microbial process development using Staphylococcus carnosus.

Shake flasks and pH-controlled small-scale bubble columns were compared with respect to their usefulness as a basic tool for process development for human calcitonin precursor fusion-protein production with Staphylococcus carnosus. Parallel control of the pH (and making use of the base addition data) is necessary to study the effects of medium composition, to identify pH-optima and to develop a medium, which minimizes the acid excretion of S. carnosus. This medium with glycerol as energy source and yeast extract as carbon and nitrogen source resulted in cell dry weight concentration in shake flasks of 5 g l(-1), which were thus improved by a factor of 10. Cell dry weight concentrations of up to 12.5 g l(-1) were measured in the batch process with pH-controlled small-scale bubble columns due to their higher oxygen transfer capability. In contrast to shake flasks it was demonstrated, that the batch process performance of recombinant S. carnosus secreting the human calcitonin precursor fusion-protein was identical within the estimation error in pH-controlled small-scale bubble columns compared to the stirred-tank reactor.

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 1(-1) of the fusion protein (420 mg 1(-1) of the recombinant hCT precursor) within 14 h, reaching 45 g 1(-1) cell dry mass with Staphylococcus carnosus in a stirred-tank reactor. Product titer and space-time yield (30 mg calcitonin precursor 1(-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 150-1 scale (scale-up factor of 50) with a minimum use of technical-grade yeast extract (40 mg fusion protein g(-1) yeast extract).