2-32: Ability of a prairie cordgrass hydrolysate to support bacterial curdlan production

Curdlan is a commercially available bacterial polysaccharide gum. It is an extracellular, high molecular weight polysaccharide synthesized by Agrobacterium sp. which is insoluble in water or acidic solutions but readily dissolves in dilute alkali solutions. Prior studies have not investigated whether curdlan can be synthesized by the bacterium Agrobacterium sp. ATCC 31749 utilizing glucose released from hydrolyzed plant biomass. Prairie cordgrass contains about 30% cellulose which can be hydrolyzed to glucose that can be utilized for bacterial curdlan production. In this study, it was determined whether Agrobacterium sp. ATCC 31749 could utilize an autoclaved and enzymatically treated prairie cordgrass hydrolysate to support curdlan synthesis. The hydrolysate was prepared by mixing milled, dried grass with 0.5% potassium phosphate buffer and then autoclaving the mixture (10% solids) at 121^oC for 30 minutes. The hydrolyzed cordgrass solids were collected by filtration, washed and dried. The treated solids were subsequently hydrolyzed using cellulase and cellobiase for 48 hours at 40^oC. The resultant filtrate was used to prepare the bacterial growth medium. The bacterial cells were grown for 120 hours at 30^oC in a medium (pH 6.8) containing the hydrolysate with the culture medium being sampled daily. The concentration of curdlan produced was monitored gravimetrically by precipitating alkali-solubilized polysaccharide using acid. It was found that the cordgrass hydrolysate could be utilized by ATCC 31749 to produce a low concentration of curdlan after 120 hours of growth. Overall, Agrobacterium sp. ATCC 31749 was capable of utilizing the autoclaved and enzymatically hydrolyzed prairie cordgrass to produce curdlan.