Effect of Intracytoplasmic Membrane Development on Oxidation of Sorbitol and Other Polyols by Gluconobacter oxydans

Abstract

By using membrane-bound dehydrogenases, Gluconobacter oxydans characteristically accomplishes single-step oxidation of many polyols and quantitative release of the oxidation product into the medium. These cells typically differentiate by forming intracytoplasmic membranes (ICM) after exponential growth on glycerol. Earlier experiments demonstrated that glycerol-grown cells containing ICM oxidized glycerol more rapidly than cells which were harvested during exponential growth and lacked ICM (Claus et al., J. Bacteriol. 123:1169J. Bacteriol. 123: -1183. This report demonstrates that ICM are also formed after growth on sorbitol. Sorbitol-grown, ICM-containing maximum stationary-phase (MSP) cells showed from 50 to 300% greater oxidation (respiration) rates on mannitol, glycerol, glucose, meso-erythritol, and meso-inositol than did exponential-phase (EXP) cells which lacked ICM. Both EXP and MSP cells exhibited maximum sorbitol oxidation at pH 5.0, 38°C, and 5% (wt/vol) sorbitol. When assayed under these optimum conditions, ICM-containing MSP cells demonstrated a 72% increase in respiration on sorbitol compared with that of EXP cells lacking ICM (oxygen quotients of 3,100 and 1,800, respectively). Gas chromatographic studies showed that sorbose was the only detectable product released from cells during oxygen quotient analysis. The specific activity of particulate-bound sorbitol dehydrogenase from ICM-containing MSP cells was twice that obtained from particulate fractions prepared from EXP cells lacking ICM. These results show that neither ICM formation after exponential growth nor increased respiration of other polyols is dependent upon the polyol used to grow cells. Our results suggest that increased respiratory activity of MSP cells is caused both by ICM formation and by increased synthesis (or activity) of the polyol dehydrogenases found in these membranes.Gluconobacter oxydans subspecies suboxydans (10), formerly called Acetobacter suboxydans, is a strict aerobe that characteristically accomplishes partial oxidation of glycols and polyols (2). Polyols or glycols must be present before growth will occur. The products of these limited oxidations rapidly and quantitatively accumulate in the growth medium, and many of these prducts have commercial value (16,28,41,45). Thus, industrial applications of these bacteria have stimulated much of the previous research on the oxidative capacities of the gluconobacters.We recently began to question the function of the limited oxidations for Gluconobacter sp. t Present address: Process Development Department, G. B. Fermentation Industries, Kingstree, SC 29556.One might reasonably assume that their rapid oxidations provide a flood of hydrogen ions to drive electron transport and oxidative phosphorylation. However, the importance of oxidative phosphorylation in the energy metabolism of Gluconobacter sp. has been questioned (21,22,40). Low P/O ratios calculated for the gluconobacters (14, 23) indicate either that they have a very inefficient mechanism for oxidative phosphorylation...

Proteomic Analysis of Ketogulonicigenium vulgare under Glutathione Reveals High Demand for Thiamin Transport and Antioxidant Protection

“…Similar change in cell morphology also occurred to G. oxydans as described previously [14] , [15] , [19] . It was reported that among the non-photosynthetic gram-negative prokaryotes, complex ICM were formed most notably in four physiological groups: Azotobacter , Gluconobacter , the obligate methane and methanol oxidizers, and the ammonium of nitrite oxidizers [15] .…”

“…Similar change in cell morphology also occurred to G. oxydans as described previously [14] , [15] , [19] . It was reported that among the non-photosynthetic gram-negative prokaryotes, complex ICM were formed most notably in four physiological groups: Azotobacter , Gluconobacter , the obligate methane and methanol oxidizers, and the ammonium of nitrite oxidizers [15] . Studies with G. oxydans showed that viable cells became two to four times longer as a result of the differentiation at the end of exponential growth by forming dense regions containing accumulations of ICM and ribosomes at the end of each cell [14] .…”

“…It was reported that G. oxydans when confronted with certain stresses could form intracytoplasmic membranes (ICM) at the end of exponential phase [14] . Accompanying the ICM formation, cells became longer and the activities of several membrane-bound dehydrogenases including glycerol [14] , sorbitol and other polyol dehydrogenases [15] were improved significantly. Improved 2-KGA production suggested probable enhanced activities of two membrane-bound dehydrogenases (sorbose dehydrogenase and sorbosone dehydrogenase) in K. vulgare responsible for the conversion of L-sorbose to 2-KGA.…”

Production of 1,3-dihydroxyacetone from glycerol by Gluconobacter oxydans ZJB09112

“…Some polyols have been reported as inducers of dehydrogenase activity in G. oxydans, and the cell's ability of bioconversion of polyols to corresponding ketone was improved [25,30]. In our preliminary work, it was found that a mixture of glycerol and mannitol affected dramatically the conversion rate of glycerol to DHA and DHA production.…”

“…Thus, a fed-batch bioprocess was developed for DHA production [1,11]. Furthermore, numerous dehydrogenases exist in G. oxydans, and some of them can be induced by polyols, such as galactitol, sorbitol, and ribitol [25,30]. Thus, optimization of the production conditions for microbial production of DHA by G. oxydans is essential.…”