PHYSICOCHEMICAL FACTORS AFFECTING THE FORMATION OF THE BIOLOGICAL RESPONSE MODIFIER SCLEROGLUCAN

The use of phosphate as the limiting nutrient for scleroglucan formati on by Sclerotium glucanicum led to stimulation of glucan formation. Fi nal exopolysaccharide concentrations achieved in phosphate-limited (18 .9 kg m-3) cultures were much higher than in the usual nitrogen-limite d fermentations (11.4 kg m-3). The mechanism by which phosphate limita tion engendered glucan formation may be largely non-specific, involvin g a generalised diversion of the carbon source away from biomass forma tion and towards glucan synthesis. The effect of stirrer speed was exa mined in a fermenter fitted with a 6-bladed Rushton turbine impeller o f 0-5 vessel diameter. It was noted that biomass and scleroglucan form ation showed different optima. This may have been due to the markedly different oxygen requirements of the two processes.