Collaborative Research: Expanding the substrate range of Clostridium thermocellum to improve understanding of its metabolism

Dartmouth College, Hanover NH

Investigators

Abstract

The dry matter in plants is called lignocellulosic biomass. It is the most abundant source of renewable raw material in the world. Converting it to fuels and products would contribute substantially to a circular bioeconomy. Unfortunately, parts of it are difficult to deconstruct, which increases costs and lowers yields. Certain microbes are capable of deconstructing lignocellulose. The objective of this project is to elucidate the metabolism of one such microbe. Once understood, efforts will be made to expand the range of substrates the organism can utilize. In parallel with the research activities, both primary investigators will work through established channels to engage K-12 students in science fairs and summer research experiences. The limited substrate range of natively cellulolytic organisms (such as C. thermocellum) makes it difficult to understand their metabolism and engineer them for applied purposes. The goal of this study is to expand the substrate range of C. thermocellum to improve our understanding of its metabolism to diagnose limitations to product formation. To accomplish this, the following set of coordinated aims will be pursued. (1) Characterize substrate transport and reversibility of central metabolism to determine factors that limit substrate range. (2) Identify mutations that allow growth on alternative substrates, using a combination of stationary-phase evolution and a combinatorial multi-substrate chemostat-based approach. (3) Use alternative growth substrates to determine factors that limit ethanol production. The work in this proposal will improve our understanding of atypical forms of glycolysis, which will expand our understanding of the possible variations of this ubiquitous and highly conserved metabolic pathway. It will improve our understanding of the factors that control substrate range in organisms, including limitations due to transport and metabolic reaction reversibility. It will also allow us to understand factors that limit product titer, a central challenge in the field of metabolic engineering. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.