Lignocellulosic materials remain one of the most abundant feedstocks for the economical production of biofuels and other value-added chemicals. Many sugars derived from such sources, however, remain unused due to poor substrate uptake. For instance, <i>Saccharomyces</i> lacks xylose-specific transporters, severely limiting its ability to effectively use these pentose sugars in engineered production pathways. In contrast, anaerobic fungi from the guts of large herbivores are able to digest a wide array of lignocellulosic feedstocks and thrive on the resulting sugars. Here, we pursued a systems-level strategy integrating transcriptomics and phenotype to mine this diverse phylum for novel sugar transporters of broad interest. A panel of gut fungi isolated from a horse, sheep, and goat, representing three distinct genera, were examined with RNAseq to generate <i>de novo</i> transcriptomes containing hundreds of putative sugar transporters. These transporters were classified on the basis of homology into families and a putative substrate was assigned. These predictions were subsequently validated through phenotypic growth studies and sugar utilization assays to reveal dozens of novel sugar transporter candidates for biotechnology. Additionally, our analysis points to several primitive class-3 G-protein coupled receptors (GPCRs) within all three gut fungal strains, which bear unexpected N-terminal domains with putative sugar binding and transport functionalities. Overall, this work reveals entirely new subsets of membrane protein transporters and receptors from nature to enhance biomass breakdown and substrate utilization.

Novel gut fungal sugar transporters for improved bioprocess efficiency

251st National Meeting (2016)

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