<b><i>Zymomonas mobilis</i> immobilized on loofa sponge: levan and ethanol production in semi-continuous fermentation

Abstract

Zymomonas mobilis is a promising microorganism in the biotechnological production of ethanol and levan due to its low biomass and high tolerance to ethanol concentrations. Ethanol and levan production by Z. mobilis CDBB-603 immobilized on loofa sponge using semi-continuous fermentation is evaluated. The first experiment, conducted with initial volume 50 mL and incubated for 24 hours, produced maximum ethanol and levan production, respectively 13.56 g L^-1 and 23.94 g L^-1, with 250 g L^-1 sucrose and without agitation, at 30°C. The second experiment was based on the best condition obtained in the first, using fermenter with production scale of 200 mL and by semi-continuous process. The second experiment also assessed immobilized biomass reuse during 10 days (240 hours) and produced higher ethanol (34.64 g L^-1) and levan (26.40 g L^-1) production rates than in the first experiment. Experiment 2 also verified that the microorganism remained viable and produced ethanol and levan until the last (10^th) recycle day.