Evaluation of a new yeast from Brazilian biodiversity, Scheffersomyces shehatae UMFG-HM 52.2, for pentose sugars conversion into bioethanol

Abstract

Hemicellulose, a heterogeneous polymer of various sugars linked with xylose backbone, is the second most available carbohydrate polymer on Earth, after cellulose. Hemicellulose can be hydrolysed by thermochemical or enzyme mediated action into a mixed sugar solution primarily composed by xylose. Bioconversion of hemicellulose derived sugars into ethanol is an important criterion to get the satisfactory overall bioethanol yield from lignocellulosic materials. However, the development of hemicellulose conversion into ethanol requires additional challenges. Only few microorganisms are able to ferment pentose sugars into ethanol. Xylose-utilizing microorganisms have shown low rates of sugar assimilation, conversion and poor tolerance to ethanol. These factors 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 into ethanol. This study showed the improved fermentation of synthetic xylose into ethanol under batch cultivations by a new strain of Scheffersomyces shehatae (UMFG-HM 52.2), isolated from Brazilian Atlantic rain forest ecosystem. Ethanol production performance of this yeast was evaluated in synthetic medium (using supplemented synthetic xylose as carbon source) in 125mL Erlenmeyer flaks at 200 rpm contained 50 mL of medium incubated for 72 h at 30°C. After 18 h of incubation, ethanol yield (Y_P/S) of 0.39 g/g and productivity (Qp) of 0.79 g/L was obtained. This study showed the potential of S. shehatae UMFG-HM 52.2 as a promising candidate in process to produce ethanol from pentose sugars.