11-69: Optimization of fermentation conditions for the ethanol production from sugarcane bagasse by Zymomonas mobilis using response surface methodology

The use of biomass as renewable sources of energy has increased industrial focus toward alternative fuel because of the depletion of fossil fuel reserves, the unstable panorama of the petrol prices, the increasing environmental and political pressures.  Also, lignocellulosics are considered as attractive raw materials for the biofuels production because of theirs availability in large quantities and low cost. In this context, sugarcane bagasse, an abundant agro-industrial residue produced in tropical countries, witch can be transformed to products with high aggregate value through pretreatments and fermentative processes, was the used raw material for the ethanol production. Initially, the bagasse suffering an acid pretreatment to extract the sugars fraction of the hemicellulose and then a deslignification to generate the cellulose available, which suffers action of an enzyme complex called cellulases, allowing the conversion to fermentable sugars. Fermentations utilizing strains of Zymomonas mobilis, in place of the traditional yeasts, have been proposed due their ethanol yields being close to theoretical and its greater potential for industrial ethanol production from sugarcane juice. The aim of this work was to study the influence between the medium components: Yeast extract, KH₂PO₄, (NH₄)₂SO₄, MgS0₄.7H₂0; and their interaction to optimize the fermentation conditions for the ethanol production from sugarcane bagasse by Z. mobilis using Simultaneous Saccharification and Fermentation technology. Statistical experimental design was used to optimize these conditions by the central composite design. The best concentrations of the medium components were 10 g/L, 3 g/L; 1.5 g/L; 1.5 g/L, respectively; achieving 55.3 g/L of ethanol.