Experimental evolution reveals an effective avenue to release catabolite repression via mutations in XylR

Christian Sievert, Lizbeth M. Nieves, Larry A. Panyon, Taylor Loeffler, Chandler Morris, Reed Cartwright, Xuan Wang, Arnold L. Demain

    Research output: Contribution to journalArticle

    4 Citations (Scopus)

    Abstract

    Microbial production of fuels and chemicals from lignocellulosic biomass provides promising biorenewable alternatives to the conventional petroleum-based products. However, heterogeneous sugar composition of lignocellulosic biomass hinders efficient microbial conversion due to carbon catabolite repression. The most abundant sugar monomers in lignocellulosic biomass materials are glucose and xylose. Although industrial Escherichia coli strains efficiently use glucose, their ability to use xylose is often repressed in the presence of glucose. Here we independently evolved three E. coli strains from the same ancestor to achieve high efficiency for xylose fermentation. Each evolved strain has a point mutation in a transcriptional activator for xylose catabolic operons, either CRP or XylR, and these mutations are demonstrated to enhance xylose fermentation by allelic replacements. Identified XylR variants (R121C and P363S) have a higher affinity to their DNA binding sites, leading to a xylose catabolic activation independent of catabolite repression control. Upon introducing these amino acid substitutions into the E. coli D-lactate producer TG114, 94% of a glucose-xylose mixture (50 g·L-1 each) was used in mineral salt media that led to a 50% increase in product titer after 96 h of fermentation. The two amino acid substitutions in XylR enhance xylose utilization and release glucose-induced repression in different E. coli hosts, including wild type, suggesting its potential wide application in industrial E. coli biocatalysts.

    Original languageEnglish (US)
    Pages (from-to)7349-7354
    Number of pages6
    JournalProceedings of the National Academy of Sciences of the United States of America
    Volume114
    Issue number28
    DOIs
    StatePublished - Jul 11 2017

    Fingerprint

    Catabolite Repression
    Xylose
    Mutation
    Escherichia coli
    Biomass
    Fermentation
    Amino Acid Substitution
    Glucose
    Petroleum
    Operon
    Point Mutation
    Minerals
    Lactic Acid
    Salts
    Binding Sites
    DNA
    Enzymes

    Keywords

    • Adaptive laboratory evolution
    • Carbon catabolite repression
    • E. coli
    • Metabolic engineering
    • XylR

    ASJC Scopus subject areas

    • General

    Cite this

    Experimental evolution reveals an effective avenue to release catabolite repression via mutations in XylR. / Sievert, Christian; Nieves, Lizbeth M.; Panyon, Larry A.; Loeffler, Taylor; Morris, Chandler; Cartwright, Reed; Wang, Xuan; Demain, Arnold L.

    In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 114, No. 28, 11.07.2017, p. 7349-7354.

    Research output: Contribution to journalArticle

    Sievert, Christian ; Nieves, Lizbeth M. ; Panyon, Larry A. ; Loeffler, Taylor ; Morris, Chandler ; Cartwright, Reed ; Wang, Xuan ; Demain, Arnold L. / Experimental evolution reveals an effective avenue to release catabolite repression via mutations in XylR. In: Proceedings of the National Academy of Sciences of the United States of America. 2017 ; Vol. 114, No. 28. pp. 7349-7354.
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