Consolidated bioprocessing of corn cob-derived hemicellulose: engineered industrialSaccharomyces cerevisiaeas efficient whole cell biocatalysts

Abstract

<jats:title>Abstract</jats:title><jats:p>Consolidated bioprocessing, which combines saccharolytic and fermentative abilities in a single microorganism, is receiving increased attention to decrease environmental and economic costs in lignocellulosic biorefineries. Nevertheless, the economic viability of lignocellulosic ethanol is also dependent of an efficient utilization of the hemicellulosic fraction, which is mainly composed of xylose and may comprise up to 40 % of the total biomass. This major bottleneck is mainly due to the necessity of chemical/enzymatic treatments to hydrolyze hemicellulose into fermentable sugars and to the fact that xylose is not readily consumed by <jats:italic>Saccharomyces cerevisiae</jats:italic> – the most used organism for large-scale ethanol production. In this work, industrial <jats:italic>S. cerevisiae</jats:italic> strains, presenting robust traits such as thermotolerance and improved resistance to inhibitors, were evaluated as hosts for the cell-surface display of hemicellulolytic enzymes and optimized xylose assimilation, aiming at the development of whole-cell biocatalysts for consolidated bioprocessing of corn cob-derived hemicellulose. These modifications allowed the direct production of ethanol from non-detoxified hemicellulosic liquor obtained by hydrothermal pretreatment of corn cob, reaching an ethanol titer of 11.1 g/L corresponding to a yield of 0.328 gram per gram of potential xylose and glucose, without the need for external hydrolytic catalysts. Also, consolidated bioprocessing of pretreated corn cob was found to be more efficient for hemicellulosic ethanol production than simultaneous saccharification and fermentation with addition of commercial hemicellulases. These results show the potential of industrial <jats:italic>S. cerevisiae</jats:italic> strains for the design of whole-cell biocatalysts and paves the way for the development of more efficient consolidated bioprocesses for lignocellulosic biomass valorization, further decreasing environmental and economic costs.</jats:p>

Sustainable biofuel production in Sub‐Saharan Africa: Exploring transesterification process, nonedible feedstocks, and policy implications

“…Biomass‐derived catalysts, such as alkali‐treated biomass, have also been investigated for their potential as heterogeneous catalysts in biodiesel production, offering a more sustainable approach as they are derived from renewable resources (Baidoo et al, 2022; da Cunha, 2021). Hybrid catalysts, combining solid metal oxides with materials like clays or activated carbon, aim to improve catalytic performance (Etim, 2022; Singh & Oraon, 2022).…”

Engineered Saccharomyces cerevisiae for lignocellulosic valorization: a review and perspectives on bioethanol production

“…Oxidoreductase and isomerase xylose consumption pathways. BGL1 ( A. aculeatus ); XylA ( A. oryzae ); Xyn ( T. reesei ) Corn cob hemicellulosic liquor (hydrothermal pretreatment) containing 26 g/L of xylose and glucose equivalents 11 0.33 [ 155 ] Cellulose+Hemicellulose CBP Cell-surface display. Industrial host.…”

“…Sakamoto and collaborators displayed BGL1 ( A. aculeatus ), XylA ( Aspergillus oryzae ), and Xyn ( T. reesei ) in the cell surface of a strain containing the oxidoreductase xylose pathway, resulting in the production of 8.2 g/L of ethanol from rice straw hemicellulose [ 154 ]. The display of the same hemicellulases on the cell surface of an industrial strain containing both isomerase and oxidoreductase xylose consumption pathways resulted in 11 g/L of ethanol from a corn cob hemicellulosic liquor [ 155 ].…”