Development of a low-cost medium for producing gellan from Sphingomonas paucimobius

This study developed an inexpensive medium for producing the exopolysaccharide gellan by growing Sphingomonas paucimobilis on the ethanol processing co-product condensed corn solubles (CCS). We acclimated S. paucimobilis to grow on a medium composed of 58.6 g/L (dry basis) CCS and 30 g/L glucose by progressive transfers in media composed of blends of the defined medium and the CCS medium. Then we varied the initial glucose concentration (0-300 g/L) in the CCS medium, and determined that 30 g/L glucose was optimal for cell population (6.0 x 1010 CFU/ml), gellan concentration (12.5 g/L), productivity (0.09 g/L/h), and yield (0.80 g/g). Benchtop bioreactor trials resulted in even higher cell numbers (4.4xl010 CFU/ml), gellan titers (13.4 g/L), productivity (0.18 g/L/h), yield (0.57 g gellan/g glucose) and glucose utilization efficiency (90%). These levels were generally higher than those obtained in the defined medium, and therefore the glucose-supplemented CCS medium is a viable alternative for commercial production of gellan.