title: Myo-inositol facilitators IolT1 and IolT2 enhance D-mannitol formation from D-fructose in Corynebacterium glutamicum.
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 Delta 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.
authors.affiliation: Institut für Biotechnologie, Forschungszentrum Jülich GmbH, Jülich, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Bäumchen
authors.forename: Eva
authors.initials: E
authors.lastname: Krings
authors.forename: Stephanie
authors.initials: S
authors.lastname: Bringer
authors.forename: Lothar
authors.initials: L
authors.lastname: Eggeling
authors.forename: Hermann
authors.initials: H
authors.lastname: Sahm
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D048230:Corynebacterium glutamicum / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism*; D007294:Inositol / Q000378:metabolism*; D008353:Mannitol / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D017384:Sequence Deletion
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D005632:Fructose; D008353:Mannitol; D007294:Inositol