Exopolysaccharide production on low-grade maple sap by Enterobacter agglomerans grown in small scale bioreactors

Enterobacter agglomerans isolated from a soil sample collected in the vicinity of a sugar house was grown on low-grade maple sap: When cultivated in shake flask, Ent. agglomerans produced exopolysaccharide and α-ketoglutarate. No polysaccharide and no α-ketoglutarate were produced during growth at dissolved oxygen concentrations lower than 1% saturation in a 3.5 1 bioreactor, but succinate, lactate and formate were accumulated. In order to increase polysaccharide production, various agitation systems were adapted to 7 1 bioreactors with working volumes of 41. Highest polysaccharide yield (Y_p/s= 0.70) and biomass yield (Y_x/s= 0.17) were obtained with bioreactors agitated with four-and six-bladed Rushton turbines. Accumulation of mixed organic acids during polysaccharide production indicated that both aerobic and anaerobic conditions prevailed inside the bioreactors. Maple sap concentration higher than 60 g 1⁻¹ (as sucrose equivalent) decreased both growth and exopolysaccharide production.