Use of Aureobasidium pullulans xylanase for simultaneous saccharification and fermentation in second- generation bioethanol production

The production of second-generation (2G) ethanol from lignocellulosic biomass is a sustainable and economically competitive alternative. Hemicellulolytic enzymatic hydrolysis can be an efficient way to degrade biomass and obtain fermentable sugars. Here, we characterized the extracellular extract of Aureobasidium pullulans UFMG-CM-Y518, and assessed its potential for the enzymatic hydrolysis of pretreated wheat straw and simultaneous saccharification and fermentation (SSF) to produce bioethanol. A. pullulans UFMG-CM-Y518 extract displayed maximum xylanase relative activity, at 40°C and pH ranging from 4.0 to 4.5. Also, presented optimal β-xylosidase activity at 80°C and pH 4.0 to 5.0, with high stability at a moderate temperature of 45°C. A. pullulans UFMG-CM-Y518 extract was evaluated in the hydrolysis of xylan and pretreated wheat straw, in simultaneous saccharification and fermentation processes for the production ethanol. The A. pullulans UFMG-CM-Y518 extract was more efficient in the hydrolysis of beechwood xylan and wheat straw, presenting efficiency 5-times higher than the commercial hemicellulase HTec2. In SSF experiments with the xylose-fermenting yeast Spathaspora passalidarum and beechwood xylan as a substrate, the A. pullulans UFMG-CM-Y518 extract efficiently degraded xylan to xylose with higher yield (66%), when compared to the separate hydrolysis. This resulted in the production of 6.6 g∙L ^− 1 ethanol with yield of 0.2 g∙g ^− 1 . A. pullulans UFMG-CM-Y518 extract improved the conversion yield of ethanol from wheat straw by Sp. passalidarum due to the increased xylose available for fermentation. In this way, we can state that this extract has potential for biotechnological applications in the biofuels industry.