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Ethanol production by Pichia stipitis immobilized on sugarcane bagasse

Abstract The search for new ethanol production technologies is due to this biofuel being a renewable and environmentally friendly option. Immobilized cell systems for ethanol production have been studied; however, the phenomenon involved in cell sorption on raw materials has been poorly explored. Therefore, this work evaluates P. stipitis immobilization on sugarcane bagasse pretreated with sulphuric acid, as well as ethanol production in batch culture. The results obtained showed that the Guggenheim-Anderson-de Boer (GAB) model explained the sorption phenomenon. The selected inoculum size for immobilization was the same as the monolayer sorption capability (1.17 gl-1). Using 1:100 g ml- 1 solid-liquid ratio, at 250 rpm, ethanol yield and productivity of 0.404 gg-1 glucose and 0.41 gl-1h-1 were obtained, respectively. The immobilized systems were stable for up to twenty-five repeated batches (36 h each). Ethanol production was increased from the first to the twenty-fifth batch (18.1 and 24.7 gl-1 ethanol). The use of complex media, such as molasses “B” or sugarcane hydrolyzates, caused an increase in process efficiency 2.4 and 1.8-fold respectively, compared with free cells systems. Biotechnological ethanol production from lignocellulosic hydrolyzates could be improved by the use of the immobilization cell sorption on pre-treated raw materials.