Curdlan is a bacterial polysaccharide gum curdlan synthesized by a species of Agrobacterium. This high molecular weight biopolymer is insoluble in water or acid but is soluble in dilute alkali. Prairie cordgrass is an excellent plant biomass to produce a glucose-containing hydrolysate since it contains approximately 30% cellulose. Using physical treatment and enzymatic hydrolysis, the cordgrass can be degraded to glucose which can support bacterial curdlan production. In this study, Agrobacterium sp. ATCC 31749 was used to determine how effectively curdlan could be produced on two types of cordgrass hydrolysates. Both hydrolysates were prepared by mixing the grass with 0.5% potassium phosphate buffer and then autoclaving the mixture (10% solids) at 121oC for 30 minutes. After autoclaving, the suspension was hydrolyzed using cellulase and cellobiase for 48 hours at 40oC and filtered. Alternatively, the cordgrass solids were collected by filtration and dried with the solids being hydrolyzed by cellulase and cellobiase for 48 hours at 40oC then filtered. The filtrates were used to make the bacterial growth media. The bacterial cells were grown for 144 hours at 30oC in a medium (pH 6.8) containing each hydrolysate with the culture medium being sampled daily. The bacterial curdlan level was monitored gravimetrically by precipitating alkali-solubilized polysaccharide with acid. ATCC 31749 produced a higher curdlan concentration after 144 hours on the hydrolysate prepared from the suspension than on the hydrolysate prepared from the solids only. In conclusion, bacterial curdlan production was shown to be affected by how each prairie cordgrass hydrolysate was prepared.
