Xylo-Oligosaccharide Utilization by Engineered Saccharomyces cerevisiae to Produce Ethanol

Abstract

The engineering of xylo-oligosaccharide-consuming Saccharomyces cerevisiae strains is a promising approach for more effective utilization of lignocellulosic biomass and the development of economic industrial fermentation processes. Extending the sugar consumption range without catabolite repression by including the metabolism of oligomers instead of only monomers would significantly improve second-generation ethanol production This review focuses on different aspects of the action mechanisms of xylan-degrading enzymes from bacteria and fungi, and their insertion in S. cerevisiae strains to obtain microbial cell factories able of consume these complex sugars and convert them to ethanol. Emphasis is given to different strategies for ethanol production from both extracellular and intracellular xylo-oligosaccharide utilization by S. cerevisiae strains. The suitability of S. cerevisiae for ethanol production combined with its genetic tractability indicates that it can play an important role in xylan bioconversion through the heterologous expression of xylanases from other microorganisms.

Metabolic engineering ofSaccharomyces cerevisiaefor second-generation ethanol production from xylo-oligosaccharides and acetate

“…Hemicellulosic-derived sugar comprises 15-35% of lignocellulosic biomass, representing a large source of renewable material that is available at a low cost (Dahlman et al, 2003; Gírio et al, 2010; Kłosowski and Mikulski, 2021). Engineered strains able to consume XOS derived from hemicellulose via intracellular hydrolysis represent a potential benefit for bioethanol production since these strains would have a competitive advantage concerning other microorganisms, such as contaminating bacteria and wild Saccharomyces and non- Saccharomyces species that are expected to be unable to utilize XOS as a carbon source (Amorim et al, 2011; Procópio et al, 2022).…”

“…One possible strategy to achieve economic 2G ethanol is to use S. cerevisiae strains genetically modified to transport and intracellularly utilize cellulose and hemicellulose-derived oligosaccharides. Such a microorganism might have a competitive advantage over other microorganisms, such as contaminating bacteria and wild Saccharomyces and non- Saccharomyces species, which are not able to metabolize oligosaccharides, as well as requiring lower amounts of hemi/cellulolytic enzymes, which should translate into a cheaper process (Procópio et al, 2022).…”

Metabolic engineering of Saccharomyces cerevisiae for second-generation ethanol production from xylo-oligosaccharides and acetate

“…Hemicellulose and cellulose play vital roles as the primary constituents in the secondary layers of wood fibre’s cell wall 6 . Together with lignin and other minor components, like extractives and minerals, they form the well-known natural composition of lignocellulose biomass 6 , 7 . Hemicellulose is a diverse group of polysaccharides that makes up 15–35% of plant biomass 6 .…”

“…Such a microorganism might have a competitive advantage over other microorganisms, such as contaminating bacteria and wild Saccharomyces and non- Saccharomyces species, which are not able to metabolize oligosaccharides. Additionally, this process may require lower amounts of hemi/cellulolytic enzymes, which should translate into an affordable process 7 .…”

Engineering Xylose Fermentation in an Industrial Yeast: Continuous Cultivation as a Tool for Selecting Improved Strains

“…With extensive use in various biotechnological applications, including first-generation biofuels, food products, biochemicals, and the pharmaceuticals industry (Nielsen, 2019), it was natural that S. cerevisiae became extended toward the use in second-generation biofuel production (Li, Chen & Nielsen, 2019). However, the use of this microorganism for energy-driven biorefineries, requires that the xylose assimilation pathway is re-constructed in this microbial cell to overcome its inability to ferment xylose (Li et al ., 2019; Procópio et al ., 2022). For instance, this microorganism has been engineered to express either xylose reductase-xylitol dehydrogenase (XR/XDH) genes (the so-called oxidoreductase pathway), the xylose isomerase (XI) gene, or selected genes from the non-phosphorylating portion of the Weimberg pathway (Jeffries, 2006; Petrovič, 2015; Jo et al ., 2017; Borgström et al ., 2019; Shen et al ., 2020; Lee et al ., 2021).…”