Premium
A thermostable mannitol‐1‐phosphate dehydrogenase is required in mannitol metabolism of the thermophilic acetogenic bacterium Thermoanaerobacter kivui
Author(s) -
Moon Jimyung,
Henke Laura,
Merz Nadine,
Basen Mirko
Publication year - 2019
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.14720
Subject(s) - thermophile , mannitol , biology , biochemistry , bacteria , alcohol dehydrogenase , dehydrogenase , enzyme , genetics
Summary Acetogenic bacteria recently attracted attention because they reduce carbon dioxide (CO 2 ) with hydrogen (H 2 ) to acetate or to other products such as ethanol. Besides gases, acetogens use a broad range of substrates, but conversion of the sugar alcohol mannitol has rarely been reported. We found that the thermophilic acetogenic bacterium Thermoanaerobacter kivui grew on mannitol with a specific growth rate of 0.33 h −1 to a final optical density (OD 600 ) of 2.2. Acetate was the major product formed. A lag phase was observed only in cultures pre‐grown on glucose, not in those pre‐grown on mannitol, indicating that mannitol metabolism is regulated. Mannitol‐1‐phosphate dehydrogenase (MtlD) activity was observed in cell‐free extracts of cells grown on mannitol only. A gene cluster (TKV_c02830–TKV_c02860) for mannitol uptake and conversion was identified in the T. kivui genome, and its involvement was confirmed by deleting the mtlD gene (TKV_c02860) encoding the key enzyme MtlD. Finally, we overexpressed mtlD , and the recombinant MtlD carried out the reduction of fructose‐6‐phosphate with NADH, at a high V MAX of 1235 U mg −1 at 65°C. The enzyme was thermostable for 40 min at 75°C, thereby representing the first characterized MtlD from a thermophile.