Myo-inositol facilitators IolT1 and IolT2 enhance d-mannitol formation from d-fructose in Corynebacterium glutamicum |
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Authors: | Carsten Bäumchen Eva Krings Stephanie Bringer Lothar Eggeling & Hermann Sahm |
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Institution: | Institut für Biotechnologie, Forschungszentrum Jülich GmbH, Jülich, Germany |
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Abstract: | Reduction of d -fructose to d -mannitol by whole-cell biotransformation with recombinant resting cells of Corynebacterium glutamicum ATCC13032 requires the coexpression of mdh and fdh , which encode mannitol and formate dehydrogenases, respectively. However, d -mannitol formation is limited by the uptake of d -fructose in its unphosphorylated form, because additional expression of the sugar facilitator from Zymomonas mobilis resulted in a significantly increased productivity. Here we identified similarities of the myo -inositol transporters IolT1 and IolT2 of C. glutamicum to the sugar facilitator of Z. mobilis . The myo -inositol transporter genes were both individually overexpressed and deleted in recombinants expressing mdh and fdh . Biotransformation experiments showed that the presence and absence, respectively, of IolT1 and IolT2 significantly influenced d -mannitol formation, indicating a d -fructose transport capability of these transporters. For further evidence, a C. glutamicum Δ ptsF mutant unable to grow with d -fructose was complemented with a heterologous fructokinase gene. This resulted in restoration of growth with d -fructose. Using overexpressed iolT1, mdh and fdh , d -mannitol formation obtained with C. glutamicum was 34.2 g L?1, as opposed to 16 g L?1 formed by the strain overexpressing only mdh and fdh , showing the suitability of myo -inositol transporters for d -fructose uptake to obtain d -mannitol formation by whole-cell biotransformation with C. glutamicum . |
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Keywords: | whole-cell biotransformation sugar transport Corynebacterium glutamicum |
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