Modulated Arabinose Uptake and cAMP Signaling Synergistically Improve Glucose and Arabinose Consumption in Recombinant Yeast

Duringthe production of ethanol from lignocellulose-derivedsugars,recombinant yeasts tend to utilize xylose and arabinose after glucoseexhaustion. So far, many glucose-insensitive pentose transportershave been reported to counteract this phenomenon, but few studieshave described intracellular factors. In this study, the combinationof adaptive evolution, comparative genomics, and genetic complementationrevealed that the hexokinase-deficient (Hxk0) arabinose-fermenting Saccharomyces cerevisiae requires the arabinose transportervariant Gal2-N376T and the mutations of guanine nucleotide exchangefactor Cdc25 to overcome glucose restriction during arabinose assimilation.The results showed that the Hxk0 recombinant yeastscould lower the metabolic/physiological threshold of cell proliferationby downregulating the intracellular cAMP levels, resulting in smallercells and increased arabinose assimilation under glucose restriction.In the medium containing 80 g/L glucose and 20 g/L arabinose, theevolved strain restoring the hexokinase activity completed fermentationat 22 h, compared to 24 h for the parental strain. Overall, the experimentalresults provide new insights into glucose repression of biorefineryyeasts.

Automated summary

During ethanol production from lignocellulose-derived sugars, recombinant yeasts preferentially utilize xylose and arabinose after glucose exhaustion. This study investigated the intracellular factors involved in this phenomenon and found that the hexokinase-deficient arabinose-fermenting Saccharomyces cerevisiae requires specific mutations in the arabinose transporter variant Gal2-N376T and the guanine nucleotide exchange factor Cdc25 to overcome glucose restriction. The results showed that these mutations downregulate intracellular cAMP levels, leading to smaller cells and increased arabinose assimilation under glucose restriction.