ALCOHOLIC FERMENTATION OF HEMICELLULOSIC HYDROLYZATE FROM SUNFLOWER CAKE BY Galactomyces geotrichum UFVJM-R10 AND Candida akabanensis UFVJM-R131
The use of the hemicellulosic fraction of plants for the production of second generation bioethanol depends on microorganisms capable to ferment pentoses. Two yeast strains habile to xylose fermenting in synthetic medium, Candida akabanensis UFVJM-R131 and Galactomyces geotrichum UFVJM-R10, not yet registered in the literature for the production of bioethanol, were evaluated here in the alcoholic fermentation of the hemicellulosic hydrolyzate from sunflower cake. The biomass hydrolysis was performed by 38 minutes at 120 °C / 1 atm with 6% H2SO4 solution and solid / liquid ratio of 1:3.2. Chromatographic characterization of the hemicellulosic hydrolyzate showed the presence of glucose (7.57 g L-1), xylose (19.53 g L-1) and arabinose (8.85 g L-1), besides 5-hydroxymethylfurfural (0.71 g L-1), furfural (0.05 g L-1) and acetic acid (5.27 g L-1). Both yeasts were able to produce ethanol from the acid hydrolyzate from sunflower cake. The fermentation carried out with G. geotrichum UFVJM-R10 and C. akabanensis UFVJM-R131 presented YP/S values of 0.29 and 0.27 g ethanol g-1sugars, respectively. The amounts of the inhibitors identified in the hydrolyzate did not affect the efficiency of the alcoholic fermentation. The supplementation of the hydrolyzate with nitrogen and mineral sources increased the rate of consumption of xylose and arabinose.