Coexpression of β-xylosidase and xylose isomerase in Saccharomyces cerevisiae improves the efficiency of saccharification and fermentation from xylo-oligosaccharides

Xylo-Oligosaccharide Utilization by Engineered Saccharomyces cerevisiae to Produce Ethanol

“…This was approximately 4 times higher than the control (a strain that expressed a single cellulase or xylanase). Although the ethanol production did not exceed that of other published works (Katahira et al, 2004;Fujii et al, 2011;Niu et al, 2019) the effective synergistic effect of those enzymes could improve the saccharification of lignocellulose and increase the ethanol yield during fermentation by S. cerevisiae.…”

“…In the earlier studies ( Katahira et al, 2004 ; Fujii et al, 2011 ; Sun et al, 2012 ), engineered S. cerevisiae strains with XR/XDH were modified by the introduction of xylanolytic enzymes. Although the authors observed ethanol production from XOS, large amounts of xylose remained in the fermentation broth, probably resulting from a redox imbalance and/or inefficient xylose uptake; this, in turn, can inhibit β-xylosidase activity ( Fujii et al, 2011 ; Peng et al, 2017 ; Niu et al, 2019 ). However, early attempts to express xylanases in engineered S. cerevisiae strains harboring XI had failed to produce ethanol from beechwood xylan (5%) as the sole carbohydrate source under aerobic growth over 28 days ( Mert et al, 2016 ).…”

“…Recently Niu et al (2019) , reported ethanol production from an efficient xylose-utilizing strain, BSPX042, expressing a xylose isomerase gene derived from a bovine rumen metagenomic study (Ru- xylA ), cloned in an episomal plasmid (pJXIH-PC, URA3 as a select marker) carrying the β-xylosidase from Penicillium oxalicum ( xyl3A ) and the signal peptide fragment INU from Kluyveromyces sp. The recombinant strain, BSGIBX, cultivated in a selective synthetic complete medium supplemented with 20 g L −1 XOS, immediately converted XOS into xylobiose and xylotriose after inoculation.…”

High Gravity Fermentation of Sugarcane Bagasse Hydrolysate by Saccharomyces pastorianus to Produce Economically Distillable Ethanol Concentrations: Necessity of Medium Components Examined

“…Second, the capability to generate the yeast cells in-fermenter within the normal fermentation timeframe eliminates the need to purchase yeast, which a cost-savings, and allows for process to be located remotely and not rely on yeast biomass delivery. Third, this process did not include the common media additions of yeast extract or peptone [21,22,31,52]. This further reduces the reliance of the process on outside sources for materials and closes the carbon balance better than when these nutrient sources are added to the fermentation but not accounted for in the carbon balance.…”

“…Alternatively, recombinant approaches have been used to genetically modify S. cerevisiae and S. pastorianus to be able to metabolize xylose directly. Many of these xylose metabolism modifications studies have not yet demonstrated higher ethanol productivity or ethanol concentrations, in part, due to using sugar concentrations that are too low in the fermentations [21,22]. Also, there have been recent gains in improving S. cerevisiae ethanol and inhibitor tolerance via recombinant means [23][24][25][26][27][28][29].…”