Elucidating the potential role of cerium-based nanomaterial in triggering activation of xylose-utilizing genes in Saccharomyces cerevisiae to convert lignocellulosic biomass into bioethanol

Abstract In this study, the primary aim was to establish an environmentally sustainable method for converting corn cob biomass waste (CCBW) into simple sugars using CeFe₃O₄NPs through the simultaneous pretreatment and hydrolysis (SPH) process at the fermenter level. The hydrolysis reaction yielded a maximum of 5.95 ± 0.102 g/L glucose and 4.22 ± 0.143 g/L xylose within 24 hours at 50°C in a 7.5-liter fermenter scale. The released sugars during the SPH process explain how CeFe₃O₄NPs work as oxidase and cellulase-hemicellulase enzymes. The study also investigates the auxiliary effect of enzymes in combination with CeFe₃O₄NPs on raw CCBW hydrolysis. Very small amounts of in-house generated cellulase-hemicellulase enzymes were used, resulting in higher glucose levels (20.10 ± 1.12 g/L) and xylose (14.9 ± 0.88 g/L) sugars being liberated. Saccharomyces cerevisiae converted these sugars into 15.2 ± 0.87 g/L of bioethanol with a productivity rate of 1.27 g/L/h using a hydrolysate. The presence of CeFe₃O₄NPs has led to the use of xylose in S. cerevisiae, a new observation that highlights the potential role of CeFe₃O₄NPs in enhancing the expression of genes responsible for xylose utilization. To confirm these results at a genetic level, transcriptomic analysis of yeast cells grown using control and CeFe₃O₄NPs- treated CCBW samples was conducted and verified by differentially expressed genes and gene ontology enrichment analysis. Up- and down-regulated genes observed in the transcriptome data were further validated using real-time PCR studies. This is the first report on such studies proving the role of CeFe₃O₄NPs in upregulating important xylose-utilizing genes, namely Xylulokinase (XKS1) and Xylose reductase (XR, YJR096W). This study could be a breakthrough in producing 2G biofuels by utilizing both C5 and C6 sugars at commercial scale.