5 years ago

Co-utilization of hexoses by a microconsortium of sugar-specific E. coli strains

Co-utilization of hexoses by a microconsortium of sugar-specific E. coli strains
Todd C. Chappell, Nikhil U. Nair
Escherichia coli is an important commercial species used for production of biofuels, biopolymers, organic acids, sugar alcohols, and natural compounds. Processed biomass and agroindustrial byproducts serve as low-cost nutrient sources and contain a variety of hexoses available for bioconversion. However, metabolism of hexose mixtures by E. coli is inefficient due to carbon catabolite repression (CCR), where the transport and catabolic activity of one or more carbon sources is repressed and/or inhibited by the transport and catabolism of another carbon source. In this work, we developed a microconsortium of different E. coli strains, each engineered to preferentially catabolize a different hexose—glucose, galactose, or mannose. We modified the specificity and preference of carbon source using a combination of rational strain design and adaptive evolution. The modifications ultimately resulted in strains that preferentially catabolized their specified sugar. Finally, comparative analysis in galactose- and mannose-rich sugar mixtures revealed that the consortium grew faster and to higher cell densities compared to the wild-type strain. Biotechnol. Bioeng. 2017;9999: 1–10. © 2017 Wiley Periodicals, Inc. Three strains of Escherichia coli were engineered to preferentially consume a different hexose-glucose, galactose, or mannose- to overcome the native inefficiencies of catabolism of sugar mixtures. Strain engineering focused on enhancing growth on the intended substrate, reducing growth on alternative substrates, and reducing growth inhibition due to native regulatory pathways. When the engineered strains were grown together, the microconsortium grew faster, and to higher final cell densities than the wildtype strain in galactose- and mannose-rich media.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/bit.26351

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