Zymomonas mobilisIFO 13 756 could take up galactose and metabolize it so that galactonic acid accumulated in the culture fluid. The oxidation of galactose was catalysed by a membrane-associated enzyme, which could be solubilized with a mixture of 1 Triton X-100 and 1mKC1. The strain also accumulated galactitol as a minor metabolite. To confer the ability to utilize galactose onZ. mobilis, a Gal+recombinant plasmid, pZG13, was constructed by the insertion of thegalETKgenes ofEscherichia coliimmediately downstream of theZ. mobilispromoter gene in pZA22, the plasmid introduced into aZymomonasstrain. Uridine diphospho-glucose 4-epimerase coded in thegalEgene was expressed inZ. mobiliscarrying pTG13. The recombinant strain could produce a small amount of ethanol from galactose.
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