Development of a fermentation process based on a defined medium for the production of pregallidermin, a nontoxic precursor of the lantibiotic gallidermin

摘要

In this work, a defined medium was developed and optimized for the mutant strain Staphylococcus gallinarum ΔP, which produces pregallidermin (PGDM), a nontoxic precursor of the lantibiotic gallidermin (GDM). The availability of a defined medium is a prerequisite for a rational process development and the investigation of medium effects on final product concentration, yield, and volumetric productivity. We identified four vitamins and three metal ions as essential for growth and PGDM production with S. gallinarum ΔP. The strain was capable of growing without any added amino acids, but the addition of proline had a strong growth-stimulatory effect. The concentrations of all essential compounds were balanced in a continuous culture using a medium-shift technique. Based on this balanced medium, a fed-batch process was developed in which S. gallinarum ΔP was grown up to a biomass concentration of 67 g l~(-1) and produced 1.95 g l~(-1) PGDM, equivalent to 0.57 mM. In the fermentation broth, we identified other GDM precursors in addition to those with a 12 or 14-amino-acid-long leader peptide that had been observed previously. Including those precursors with shorter leader sequences, the final concentration would correspond to 0.69 mM. In molar terms, this represents a roughly fourfold or fivefold increase, respectively, over established, complex medium-based gallidermin production processes (Kempf et al. 2000). With the same medium and feed protocol, the maximum concentration of mature GDM produced by wild-type S. gallinarum Tü 3928 was only 0.08 mM.