17-13: Identification of redundancies in the xylose utilization pathway in the filamentous fungus Aspergillus oryzae

Pentose sugars are a major building block of plant biomass, however, there is a paucity of information regarding how pentose sugars are processed by microbes, and bioprocess organisms are often unable to utilize these sugars efficiently or even at all. The ability to rapidly improve pentose utilization in industrial strains will lead to increased carbon efficiency within the biorefinery. With this in mind, the goals of this research were to increase our understanding of how microbes utilize pentose sugars and to generate methods for increasing utilization of pentose sugars in Aspergillus oryzae.

Initially, metabolic modeling identified genes potentially involved in xylose utilization. Targeted gene knock-out and over-expression methods were used to determine the role of these candidate genes in xylose metabolism. Reductions in utilization were observed for individual knockouts of the annotated xylose reductase (XR) and xylitol dehydrogenase (XDH) genes, however, significant xylose utilization still occurs after deletion of each of these genes, (61% and 78% of wild type respectively), indicating that other enzymes capable of performing the same functions are present. The effect of deletion of potentially redundant xylose utilization genes is being investigated. For example, deletion of a gene annotated as an arabinitol dehydrogenase (AolDH) in the xylitol dehydrogenase deletion background resulted in a decrease from 78% with the single XDH deletion to 16% of wild type xylose utilization with the double XDH/AolDH mutant. The results of deletions of other potentially redundant genes will also be presented.