Resumo

Brazil produced 28.5 million liters of ethanol in 2010/2011. The second generation ethanol production from lignocellulosic biomass along with the cane juice derived ethanol is an evident point of economic and social perspectives in Brazil. It is noteworthy that the production of sugarcane in Brazil was approximately 75,000 million tons in 2010/201. Hemicellulose is the second largest abundant carbohydrate source on Earth after cellulose. Bioconversion of hemicellulose derived sugars to ethanol is an important criterion to get the satisfactory overall ethanol yield during fermentation. However, the development of hemicellulose conversion into ethanol requires additional challenges. Microorganisms for pentose sugars conversion into ethanol are scanty and only few microorganisms are known as yet. There are few microorganisms available that ferment pentose sugars to ethanol. However their low rates of sugars assimilation, conversion and poor tolerance to ethanol are still important factors that often prevent their use in technological processes at large scale. In this line, the search for new microorganisms that efficiently assimilate pentoses, particularly xylose, is a priority within the context of the integral use of lignocellulosic biomass. This study showed the improved fermentation of xylose into ethanol by a new species of yeast (Candida shehatae UFMG HM 52.2), isolated from Brazilian ecosystems. Ethanol production performance of this yeast was evaluated in synthetic medium (37 g/L of xylose supplemented with 5g/L of ammonium sulphate, 3g/L of yeast extract and 3g/L of malt extract). The fermentation was carried out in 125mL Erlenmeyer flaks at 200 rpm contained 50 mL of the synthetic medium. Inoculum of Candida shehatae UFMG HM 52.2 (0.5 g/L cells) was transferred aseptically into xylose supplemented synthetic medium and subsequently incubated for 72 h at 30°C. After 18 h of incubation, ethanol yield (YP/S) of 0.32 g/g and productivity (Qp) of 0.74 g/L was obtained. This study showed the high feasibility to use Candida shehatae UFMG HM 52.2 as a promising candidate in process to produce ethanol from pentose sugars. Acknowledgments: FAPESP-BIOEN, CAPES and CNPq