Influence of the glucose concentration on the yield of biomass and lipopolysaccharide in Salmonella cultures

Abstract

Two Salmonella S-forms and two R-mutants were cultivated in complex medium supplemented with different amounts (0.5-3%) glucose. Cultivation was performed batchwise in a fermentor under aerobic conditions. With all strains investigated, the yield of bacterial mass increased with increasing concentration of glucose. In the case of three strains, the % LPS content of bacteria also increased, thus achieving the aim of this investigation. The synthesis of bacterial mass and LPS did not proceed in parallel and differed from strain to strain. At optimal glucose concentration, the yield of LPS could be increased up to 250%. The chemical composition of the LPS was independent of the glucose concentration. The individual strains exhibited an identical composition with regard to lipid A and polysaccharide when cultured at different glucose concentrations. The uniformity of the molecular distribution of LPS could also be confirmed by SDS-polyacrylamide gel electrophoresis. In the S-form LPSs, also the proportion of the unsubstituted R-form LPS was not affected by the glucose concentration in the culture medium. The present results demonstrate that optimisation of the cultivation conditions with respect to the glucose concentration of the medium would be of advantage especially for Salmonella strains that are cultivated frequently.