Hemicellulosic biomass is an abundant waste material that can serve as an ideal carbon source in the process of generating high value chemicals. The hydrolysis of hemicellulose results primarily in glucose and xylose, two sugars that Escherichia coli can use for both growth and product formation. Due to catabolic repression, wild-type E. coli will preferentially use glucose over xylose, resulting in sequential and inefficient use of the total available carbon in mixed-sugar systems. To overcome this obstacle, we propose the co-culture growth of a wild-type E. coli strain that preferentially uses glucose with a high-density achieving xylose-specialist strain. The xylose-specialist strain includes several gene deletions in its glucose metabolism pathway. Both strains were engineered to generate violacein, a purple pigment with antibiotic properties. Because the strains are predicted to behave as specialists for glucose or xylose under mixed-sugar conditions, we tested whether the co-culture would address the inefficiencies observed with the wild-type strain alone. We have observed that the co-culture of a wild-type glucose-preferential strain with a xylose-specialist strain increases the final titer of violacein and achieves higher total carbon consumption in mixed sugar systems than the wild-type strain alone. We will also describe ongoing efforts to characterize and optimize co-culture growth and violacein production. This work has the potential to generate an economically relevant novel platform for the co-utilization of sugar mixtures to produce target chemicals.

Co-Culture of Engineered Escherichia coli for Violacein Production from Hemicellulosic Sugars

2019 Spring National Meeting

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