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Biotechnol Lett. 2012 Oct;34(10):1825-32. doi: 10.1007/s10529-012-0970-z. Epub 2012 Jun 6.

Engineering efficient xylose metabolism into an acetic acid-tolerant Zymomonas mobilis strain by introducing adaptation-induced mutations.

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School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, GA 30332-0100, USA.


The impact of the two adaptation-induced mutations in an improved xylose-fermenting Zymomonas mobilis strain was investigated. The chromosomal mutation at the xylose reductase gene was critical to xylose metabolism by reducing xylitol formation. Together with the plasmid-borne mutation impacting xylose isomerase activity, these two mutations accounted for 80 % of the improvement achieved by adaptation. To generate a strain fermenting xylose in the presence of high acetic acid concentrations, we transferred the two mutations to an acetic acid-tolerant strain. The resulting strain fermented glucose + xylose (each at 5 % w/v) with 1 % (w/v) acetic acid at pH 5.8 to completion with an ethanol yield of 93.4 %, outperforming other reported strains. This work demonstrated the power of applying molecular understanding in strain improvement.

[Indexed for MEDLINE]

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