Zymomonas mobilis immobilized on loofa sponge and sugarcane bagasse for levan and ethanol production using repeated batch fermentation

Abstract

Two experiments were carried out using loofa sponge and sugarcane bagasse as immobilization support. First a 2(5-2) design of experiments was realized with the following independent variables: sucrose concentration; pH; incubation time and agitation. Based on the best results observed in this experiment, the capacity for reuse of the supports in subsequent fermentations was evaluated for 12 recycle days. Loofa sponge support was the best immobilization support and in the 2(5-2) experiment, it showed 2.58 g.L-1 of immobilized cells and 19.13 g.L-1 of exopolysaccharide levan. Sugarcane bagasse showed the highest ethanol production (103.82 g.L-1). In the immobilization support recycling experiment, sugarcane bagasse was the most promising support since it showed cell viability up to the last fermentation cycle, confirmed by scanning electronic microscopy, also showing the largest values for immobilized biomass (3.23 g.L-1), levan (32.13 g.L-1), ethanol (148.18 g.L-1) and sucrose consumption (92.64%).