P39: Curdlan production by a curdlan overproducer mutant grown on a prairie cordgrass hydrolysate

The bacterial polysaccharide gum curdlan is a biopolymer synthesized by a species of Agrobacterium. The gum is a high molecular weight polysaccharide that is insoluble in water or acid but is soluble in dilute alkali. A prior study has reported the isolation of a curdlan overproducer mutant of Agrobacterium sp. ATCC 31749. Prairie cordgrass is a plant that is composed of approximately 30% cellulose. Degradation of its cellulose using physical treatment and enzymatic hydrolysis produces glucose which provides an excellent substrate for bacterial curdlan production. In this study, the Agrobacterium sp. curdlan overproducer was used to determine how effectively curdlan could be produced on a cordgrass hydrolysate. The hydrolysate was prepared by mixing the grass with 0.5% potassium phosphate buffer and then autoclaving the mixture (10% solids) at 121^oC for 30 minutes. After the autoclaved cordgrass solids were collected by filtration and dried, the solids were hydrolyzed using cellulase and cellobiase for 48 hours at 40^oC and filtered. The filtrate was used to make the bacterial growth medium.  The mutant cells were grown for 144 hours at 30^oC in a medium (pH 6.8) containing the hydrolysate with the culture medium being sampled daily. The curdlan level synthesized by the mutant was monitored gravimetrically by precipitating alkali-solubilized polysaccharide using acid. It was observed that the cordgrass hydrolysate was utilized by the mutant to produce a high curdlan concentration after 144 hours of growth. In conclusion, the curdlan overproducer mutant produced a significant concentration of polysaccharide from the hydrolyzed prairie cordgrass.