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Appl. Environ. Microbiol., 12 1996, 4465-4470, Vol 62, No. 12
K Deanda, M Zhang, C Eddy and S Picataggio
The substrate fermentation range of the ethanologenic bacterium Zymomonas
mobilis was expanded to include the pentose sugar, L- arabinose, which is
commonly found in agricultural residues and other lignocellulosic biomass.
Five genes, encoding L-arabinose isomerase (araA), L-ribulokinase (araB),
L-ribulose-5-phosphate-4-epimerase (araD), transaldolase (talB), and
transketolase (tktA), were isolated from Escherichia coli and introduced
into Z. mobilis under the control of constitutive promoters that permitted
their expression even in the presence of glucose. The engineered strain
grew on and produced ethanol from L-arabinose as a sole C source at 98% of
the maximum theoretical ethanol yield, based on the amount of consumed
sugar. This indicates that arabinose was metabolized almost exclusively to
ethanol as the sole fermentation product, with little by-product formation.
Although no diauxic growth pattern was evident, the microorganism
preferentially utilized glucose before arabinose, apparently reflecting the
specificity of the indigenous facilitated diffusion transport system. This
microorganism may be useful, along with the previously developed
xylose-fermenting Z. mobilis (M. Zhang, C. Eddy, K. Deanda, M. Finkelstein,
and S. Picataggio, Science 267:240-243, 1995), in a mixed culture for
efficient fermentation of the predominant hexose and pentose sugars in
agricultural residues and other lignocellulosic feedstocks to ethanol.
Copyright © 1996, American Society for Microbiology
Development of an arabinose-fermenting Zymomonas mobilis strain by metabolic pathway engineering
National Renewable Energy Laboratory, Golden, Colorado 80401, USA.
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