<b>Ethanol and Levan production by sequential bath using <i>Zymomonas mobilis</i> immobilized on alginate and chitosan beads

Abstract

Current study evaluates ethanol and levan production using Zymomonas mobilis immobilized on alginate and chitosan beads and assesses the capacity of the beads for reuse in sequential fermentations. Two experiments were carried out: In the first experiment 2^(5-2) design evaluated the following independent variables: sucrose concentration; pH; incubation time; temperature and agitation. In the second experiment, based on the best conditions observed in 2^(5-2), the capacity of the immobilization support reuse in subsequent fermentations was evaluated for 12 days. In experiments using fractionated factorial experimental design 2^(5-2) the best results by immobilized biomass (2.6 g L^-1) and immobilization efficiency was shown by alginate and chitosan beads showed only 0.22 g L^-1. Chitosan support provided the best rates to levan production (8.90 g L^-1). Alginate support showed the highest values by ethanol production (93.4 g L^-1). In batch sequential fermentation, re-using immobilization support, alginate support was efficient by maintaining the cellular viability on immobilized support (0.94 g L^-1), levan production (21.11 g L^-1) and ethanol production (87.21 g L^-1). Chitosan support was inadequate for sequential batches since the beads dissolved after the second cycle.