Xanthan Biopolymer Semipilot Fermentation

Using standard microbiological techniques in a semipilot plant-scalable fermenter, xanthan-specific culture techniques developed by the U.S. Dept of Agriculture's Northern Regional Research Laboratory (NRRL) were used at Marathon Oil Co.'s Denver Research Center (DRC) to obtain improved and reproducible high conversions and yields of xanthan biopolymer broth. Practical nutrients and fermenter parameters were studied to define and improve the viscosity performance and economics of xanthan broth production for thickening water in the Maraflood(TM) enhanced oil recovery process. Introduction Xanthan gum biopolymer shows promise for enhanced oil recovery. One of its current major uses is in drilling muds. After a preliminary review of its characteristics and potential for manufacture by fermentation, a scalable laboratory pilot study was conducted at DRC to evaluate the suitability of several feedstocks and bacterial organisms.Our fermentation results confirm NRRL procedures and recommendations for this bacterial fermentation and indicate a number of practical feedstocks for producing high-viscosity broths. We can reproduce xanthan broths as viscous as those previously furnished to us by NRRL and various commercial suppliers interested in this potential market for enhanced oil recovery. Initial economic estimates indicate that xanthan broths can be made for about one-half the price of commercially available biopolymer.Our research to date on the biopolymer xanthan gum and fermentation broth is summarized. This includes the chemical and physical properties, synergistic interactions, salinity effects, physical and chemical modifications, chemical and biological stabilities, mobility control properties, and oil recovery performances in cores. Experimental results indicate that broad ranges of readily available carbohydrate and nitrogen sources are suitable and economical alternative substrates for this fermentation. Dissolved oxygen concentration and oxygen usage are practical parameters for monitoring the fermentation. Experimental Carbon and nitrogen sources from several commercial suppliers were screened. Staleydex(TM) 333 dextrose (a carbon source) and Brown-Forman corndistillers dried solubles (DDS) (a nitrogen source) were selected for reproducibility studies. Enzose E-084 cornstarch hydrolysate and Argo(TM) corn steep were furnished by Corn Products Corp.Several recommended strains of Xanthomonas campestris were obtained from the American Type Culture Bank and the NRRL in Peoria, IL. The strain selected for most of our investigation was NRRL B-1459-4L. A sample of Xanthomonas manihotis from the American Type Culture Bank also was evaluated. Apparatus A Psycrotherm controlled environmental incubator shaker was used to culture cells on plates and in liquid inocula. A 14-L Microferm(TM) fermenter obtained from the New Brunswick Scientific Co. (Fig. 1) had stirring, aeration, temperature control, pressure control, foam control, and pH control. SPEJ P. 205^