Effect of yeast extract addition to a mineral salts medium containing hydrolyzed plant xylan on fungal pullulan production.

The ability of the fungus Aureobasidium pullulans ATCC 42023 to produce pullulan from yeast extract-supplemented xylan hydrolysates of the prairie grass prairie cordgrass was examined relative to polysaccharide and cell biomass production, yield, and pullulan content of the polysaccharide. A pullulan concentration of 11.2 g L-1 and yield of 0.79 g g-1 was produced by ATCC 42023 when grown for 168 h at 30°C on the phosphate-buffered hydrolysate supplemented with yeast extract. The highest biomass level being 8.8 g L-1 was produced by ATCC 42023 after 168 h on a yeast extract-supplemented, hydrolysate-containing complete medium lacking sodium chloride. The highest pullulan content of the polysaccharide produced by ATCC 42023 after 168 h on the hydrolysate medium supplemented with yeast extract and ammonium sulfate was 70%. The findings indicate that a polysaccharide with a high pullulan content can be produced at a relatively high yield by the fungus grown on a yeast extract-supplemented xylan hydrolysate, suggesting that pullulan could be produced using a biomass-based process.