Effect of the nitrogen source on biosynthesis of exopolysaccharides and activity of carbon metabolism enzymes in Aureobasidium pullulans

The Aureobasidium pullulans (de Bary) Arnaud population is known to be heterogeneous with respect to genotypic characteristics and a nitrogen source optimal for the production of exopolysaccharides. (NH4)(2)SO4 and NaNO3 were found to be the optimal nitrogen sources for A. pullulans strains 11 (genotypic group I) and F-448 (the genotypic group II), respectively. Cells of A. pullulans 11 (a producer of pullulan) grown in medium with (NH4)(2)SO4 as a nitrogen source exhibited higher activities of all carbon metabolism enzymes tested (glucose-6-phosphate dehydrogenase, NADP- and NAD-dependent 6-phosphogluconate dehydrogenase, malate dehydrogenase, phosphoglucomutase, phosphofructokinase, fructose-diphosphate aldolase, phosphoenolpyruvate carboxykinase, citrate synthase, isocitrate dehydrogenase, and NADP- and NAD-dependent malic enzymes) as compared to cells grown in medium with NaNO3. A reverse enzyme activity pattern was observed for strain F-448 (a producer of aubasidan). These effects of nitrogen sources are discussed in relation to nitrogen assimilation pathways and possible application for the characterization of a new intraspecific taxon of A. pullulans.