A rationally identified marine GH1 β-glucosidase has distinguishing functional features for simultaneous saccharification and fermentation
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The classical route for second-generation ethanol from lignocellulosic biomass is hampered by high process costs, fostering the development of alternative strategies such as simultaneous saccharification and fermentation (SSF). However, the lack of compatible enzyme cocktails poses a challenge. In this study, the enzyme EmBgl from the marine bacterium Exiguobacterium marinum was rationally identified based on structural and phylogenetic analyses, known desirable properties of close orthologs, and the ecological niche of its organism source. EmBgl is a multifunctional and glucose-tolerant enzyme that efficiently hydrolyzes cello-oligosaccharides due to a positive-subsite region that can accommodate long cello-oligosaccharides without imposing steric impediments. The efficacy of EmBgl in an SSF process was demonstrated using pretreated sugarcane bagasse as feedstock, yielding 28 gL−1 of ethanol in 30 h. The distinguishing functional properties of EmBgl and its successful utilization in an SSF process highlight its potential in biotechnological applications in which lignocellulose deconstruction is desirable under milder temperatures.