Avaliação de suportes para a imobilização de Zymomonas mobilis CCT 4494 visando à produção de etanol e levana

• Autor(a) principal: Santos, Vidiany Aparecida Queiroz [UNESP]
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/110990
• topic: Biotecnologia; Álcool - Indústria; Zymomonas mobilis; Celulas imobilizadas; Frutanos; Biotecnologia

Zymomonas mobilis is considered to have high biotechnological potential for ethanol and levan production, because it produces little biomass and shows good tolerance to ethanol concentrations. However, this efficiency can be decreased if the free cells are exposed to unfavorable conditions during conventional fermentations. Cell immobilization is an alternative to solve this problem and offers numerous advantages such as higher cell concentrations, greater stability and improved production. Thus the aim of this work was to select a suitable support for the immobilization of Zymomonas mobilis in order to increase the production of ethanol and levan from sucrose as the carbon source. The optimum values for ethanol and levan production were determined using response surface methodology (RSM). The first experiment was a 2(5-2) design with the following independent variables: sucrose concentration, pH, incubation time, temperature and agitation of the culture medium. Based on the best conditions observed in the 2(5-2) experiment, reuse of the support was evaluated during 12 days of fermentation. Ethanol production was determined by microdiffusion and the levan production on fructose units after acid hydrolysis. The biomass was determined by optical density at 570 nm and microbial growth on the support was verified by scanning electron microscopy. In the 2(5-2) experiment the loofa sponge was the best support for immobilization with the highest values for immobilized biomass (2.95 g/L); levan production (24.9 g/L) and ethanol production (50.95 g/L). In the immobilization support reuse experiments in batch fermentations, all the supports evaluated could be reused for 12 cycles, with the exception of chitosan beads. Sugarcane bagasse was shown to be the best substrate for microbial adhesion (3.23 g/L) and for levan (32.13 g/L) and ethanol production (36.50 g/L). Thus the loofa sponge and sugarcane bagasse represented the most promising support ...