Production of biofuels from lignocellulosic (LC) residues should be fuelling the energy matrix in the near future. Yeasts will play an important role as platform microorganisms for the conversion processes of LC-derived sugars into, for instance, fuel ethanol but also other advanced fuels and chemicals. Fermentation of LC hydrolysates poses many scientific and technological challenges. For example, the limitation of Saccharomyces cerevisiae in fermenting pentose sugars (derived-hemicellulose), and the pre-treatment processes that generate various yeast growth inhibitors (furan-derivatives, phenolics, and organic acids), reduce the efficiency of fermentation. To overcome the inability of the S. cerevisiae to ferment xylose and also xylo-oligosaccharides (XOS) and, to tackle the inhibition by acetic acid, this present research proposal aims to engineer and to improve the performance of these pathways in industrial S. cerevisiae strains (SA-1). For that, genes of XOS transport and dissimilation and a NADH-consuming acetate pathway will be engineered in a xylose-consuming yeast strain. The strains will be engineered using a recently developed high-efficient CRISPR/Cas9 system-based approach for industrial S. cerevisiae genome editing. For the construction of the xylose consumption pathway, the xylose reductase and xylitol dehydrogenase genes (XR/XDH) from Scheffersomyces stipitis were used. The XOS transport and consumption genes from Neurospora crassa will be used for reconstitution of this XOS utilization pathway in this xylose-consuming strain. Moreover, the overexpression of the acetyl-CoA synthetase (ACS) gene from Salmonelas enterica will be used to increase conversion of acetate into acetyl-CoA and the heterologous expression of the acetylating acetaldehyde dehydrogenase (AADH) gene from Escherichia coli will be used to enable the conversion of acetyl-CoA into acetaldehyde. The transformed strains will be evaluated under anaerobic conditions according to their capacity to consume xylose, XOS, and acetate. The consumption of XOS and acetate will expand the capabilities of S. cerevisiae to utilize plant-derived and represent the potential to increase the efficiency of second-generation biofuel production.
News published in Agência FAPESP Newsletter about the scholarship: