Molecular Properties of Membrane-Bound FAD-ContainingD-Sorbitol Dehydrogenase from ThermotolerantGluconobacter frateuriiIsolated from Thailand

Characterization of Genes Involved inD-Sorbitol Oxidation in ThermotolerantGluconobacter frateurii

“…Cells cultured for appropriate periods were harvested, washed, and disrupted by passing them through a French pressure cell press (American Instruments, Silver Spring, MD), as described previously. 6) After the intact cells were removed by centrifugation, the supernatants were ultracentrifuged at 100;000 g for 60 min. The resulting precipitate was resuspended in McIlvaine buffer (McB, pH 5.0) and used as membrane fraction, while the supernatant was used as soluble fraction.…”

“…Two membrane-bound enzymes involved in L-sorbose production have been reported and characterized, one containing pyrroloquinoline quinone (PQQ) and the other containing FAD as prosthetic group. [5][6][7] The former enzyme is identical to the well-known glycerol dehydrogenase PQQ-GLDH, the substrate specificity of which is relatively versatile but stereo-and regio-specific.…”

“…8) On the other hand, membrane-bound Dsorbitol dehydrogenase with FAD as the prosthetic group, FAD-SLDH, reacts more specifically with Dsorbitol than PQQ-GLDH does, and consists of three subunits, small, large, and cytochrome c subunits, the corresponding genes of which are sldS, sldL, sldC respectively. 6) Both enzymes react with D-sorbitol to produce L-sorbose, and the reducing equivalents obtained are passed to ubiquinone, that is, they catalyze a similar reaction. In a previous study, therefore, we attempted to elucidate the difference in physiological roles of these enzymes in D-sorbitol oxidation in a thermotolerant strain, G. frateurii THD32.…”

Use of aGluconobacter frateuriiMutant to Prevent Dihydroxyacetone Accumulation during Glyceric Acid Production from Glycerol

“…In this study, in an effort to eliminate DHA accumulation, we examined GA production using a mutant of G. frateurii THD32, which is defective in PQQ-GLDH (ÁsldA). 16) G. frateurii THD32 17) and G. frateurii ÁsldA (sldA::Km) 16) were precultivated in 5 ml of medium containing 5 g/l of glucose, 5 g/l of polypepton (Nihon Pharmaceutical, Tokyo), 5 g/l of yeast extract (Difco Laboratories, Detroit, MI), and 1 g/l of MgSO 4 . 7H 2 O at 30…”

“…Hence G. frateurii THD32 17) and its ÁsldA mutant 16) were investigated for their ability to grow on several concentrations of glycerol (5-20% w/v) and to produce GA, because the ÁsldA mutant of THD32, the same species as NBRC103465, had already been constructed by Soemphol et al 16) First, using flasks we examined the effects of the initial glycerol concentration on growth and GA production ( Table 1). Wild-type strain THD32 showed OD 600 of 3.9 and 3.2 and produced 20.1 and 25.6 g/l of GA on 100 and 150 g/l of glycerol respectively after 4 d of incubation.…”