P22: Fungal pullulan production from prairie cordgrass hydrolysate

The polysaccharide gum pullulan is a commercially available polysaccharide that has a number of applications due to its being water-soluble. Pullulan can be produced from a number of carbon sources including xylose. A novel approach to synthesize pullulan would be to produce pullulan from the xylose released from hydrolyzed plant biomass. Prairie grasses represent a potential source of plant biomass that could be utilized. These grasses produce a high yield with minimal fertilizer input and they contain a very high fiber content indicating a high hemicellulose level. Currently, prairie grasses, including prairie cordgrass, are used for grazing by livestock or harvested as hay for foraging by livestock. In this study, the ability of the pullulan-producing fungus Aureobasidium pullulans ATCC 42023 to utilize a prairie cordgrass hydrolysate to synthesize pullulan was investigated. A hydrolysate of prairie cordgrass was prepared treating the ground, dried grass with an alkaline hydrogen peroxide solution for 24 hours and then hydrolyzing it with a thermostable xylanase.  The fungal cells were grown in a phosphate-buffered medium (pH 6.0) containing prairie cordgrass hydrolysate in shake flask cultures.  The strain was grown for 192 hours at 30^oC. The concentration of pullulan produced was measured gravimetrically. It was determined that ATCC 42023 synthesized the highest pullulan level after 192 hours of growth on the medium. In conclusion, it was found that the fungus A. pullulans ATCC 42023 could utilize hydrolyzed prairie cordgrass to produce pullulan.