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1.
Asymmetric oxidation by Gluconobacter oxydans   总被引:1,自引:0,他引:1  
Asymmetric oxidation is of great value and a major interest in both research and application. This review focuses on asymmetric oxidation of organic compounds by Gluconobacter oxydans. The microbe can be used for bioproduction of several kinds of important chiral compounds, such as vitamin C, 6-(2-hydroxyethyl)amino-6-deoxy-α-l-sorbofuranose, (S)-2-methylbutanoic acid, (R)-2-hydroxy-propionic acid and 5-keto-d-gluconic acid. Characteristics of the bacteria and research progress on the enantioselective biotransformation process are introduced.  相似文献   

2.
Summary The influence of culture pH on the metabolism of Gluconobacter oxydans was determined. An acidic milieu during growth of the organism enhances the oxidation rate. The CO2 evolution rate representing the assimilation of the product is inhibited by a low pH value. Growth of the bacteria is possible both on glycerol and DHA in separate phases, which is not a controlled as diauxic growth. Product formation follows Luedeking-Piret kinetics.now: Institut für Biotechnologie, TU Graz, Petersgasse 12, 8010 Graz, Austria  相似文献   

3.
Summary The mode of electron transport associated with the dehydrogenase enzymes located on the cytoplasmic membrane inGluconobacter oxydans (ATCC 9937) has been postulated. High turnover of dehydrogenases under oxygen enrichment conditions is explained on the basis of a simplistic electron transport chain comprising cytochrome c553 (MW 23000) as a subunit of dehydrogenase and a cytochrome b562. The electron transport chain under low dissolved oxygen tension (DOT) is shown to comprise a number of cytochrome c species with very low midpoint potential difference.  相似文献   

4.
Summary Gluconobacter oxydans subspecies suboxydans (ATCC 621 H), when growing at high glucose concentrations, oxidizes this substrate incompletely and gluconic acid accumulates in the medium in almost stoichiometric amounts. Such cells were harvested and entrapped in various alginate gels. The preparation with the highest retention of glucose oxidizing activity was used in further studies with the aim of developing an efficient process for continuous gluconic acid production.The retention of activity increases (up to 95%) as the alginate concentration in the gel decreases or the cell/alginate weight ratio is enhanced. In the latter case, however, transport of oxygen to and inside the biocatalyst beads rapidly becomes rate-limiting and thus lowers the efficiency of the biocatalyst. Similarly, the efficiency decreases as the size of the biocatalyst beads increases. In no case rate-limitation by transport of glucose was found. Thus, biocatalyst activity per unit volume of support, diameter of the biocatalyst beads, and aeration efficiency are important parameters for reactor design.  相似文献   

5.
Gluconobacter oxydans is well known for the limited oxidation of compounds and rapid excretion of industrially important oxidation products. The dehydrogenases responsible for these oxidations are reportedly bound to the cell's plasma membrane. This report demonstrates that fully viable G. oxydans differentiates at the end of exponential growth by forming dense regions at the end of each cell observed with the light microscope. When these cells were thin sectioned, their polar regions contained accumulations of intracytoplasmic membranes and ribosomes not found in undifferentiated exponentially growing cells. Both freeze-fracture-etched whole cells and thin sections through broken-cell envelopes of differentiated cells demonstrate that intracytoplasmic membranes occur as a polar accumulation of vesicles that are attached to the plasma membrane. When cells were tested for the activity of the plasma membrane-associated glycerol dehydrogenase, those containing intracytoplasmic membranes were 100% more active than cells lacking these membranes. These results suggest that intracytoplasmic membranes are formed by continued plasma membrane synthesis at the end of active cell division.  相似文献   

6.
A bacterium isolated from patulin-contaminated apples was capable of degrading patulin to a less-toxic compound, ascladiol. The bacterium was identified as Gluconobacter oxydans by 16S rRNA gene sequencing, whereas ascladiol was identified by liquid chromatography-tandem mass spectrometry and proton and carbon nuclear magnetic resonance. Degradation of up to 96% of patulin was observed in apple juices containing up to 800 microg/ml of patulin and incubated with G. oxydans.  相似文献   

7.
Gluconobacter oxydans: its biotechnological applications   总被引:1,自引:0,他引:1  
Gluconobacter oxydans is a gram-negative bacterium belonging to the family Acetobacteraceae. G. oxydans is an obligate aerobe, having a respiratory type of metabolism using oxygen as the terminal electron acceptor. Gluconobacter strains flourish in sugary niches e.g. ripe grapes, apples, dates, garden soil, baker's soil, honeybees, fruit, cider, beer, wine. Gluconobacter strains are non-pathogenic towards man and other animals but are capable of causing bacterial rot of apples and pears accompanied by various shades of browning. Several soluble and particulate polyol dehydrogenases have been described. The organism brings about the incomplete oxidation of sugars, alcohols and acids. Incomplete oxidation leads to nearly quantitative yields of the oxidation products making G. oxydans important for industrial use. Gluconobacter strains can be used industrially to produce L-sorbose from D-sorbitol; D-gluconic acid, 5-keto- and 2-ketogluconic acids from D-glucose; and dihydroxyacetone from glycerol. It is primarily known as a ketogenic bacterium due to 2,5-diketogluconic acid formation from D-glucose. Extensive fermentation studies have been performed to characterize its direct glucose oxidation, sorbitol oxidation, and glycerol oxidation. The enzymes involved have been purified and characterized, and molecular studies have been performed to understand these processes at the molecular level. Its possible application in biosensor technology has also been worked out. Several workers have explained its basic and applied aspects. In the present paper, its different biotechnological applications, basic biochemistry and molecular biology studies are reviewed.  相似文献   

8.
Gluconobacter oxydans, like all acetic acid bacteria, has several membrane-bound dehydrogenases, which oxidize a multitude of alcohols and polyols in a stereo- and regio-selective manner. Many membrane-bound dehydrogenases have been purified from various acetic acid bacteria, but in most cases without reporting associated sequence information. We constructed clean deletions of all membrane-bound dehydrogenases in G. oxydans 621H and investigated the resulting changes in carbon utilization and physiology of the organism during growth on fructose, mannitol, and glucose. Furthermore, we studied the substrate oxidation spectra of a set of strains where the membrane-bound dehydrogenases were consecutively deleted using a newly developed whole-cell 2,6-dichlorophenolindophenol (DCPIP) activity assay in microtiter plates. This allowed a detailed and comprehensive in vivo characterization of each membrane-bound dehydrogenase in terms of substrate specificity. The assays revealed that general rules can be established for some of the enzymes and extended the known substrate spectra of some enzymes. It was also possible to assign proteins whose purification and characterization had been reported previously, to their corresponding genes. Our data demonstrate that there are less membrane-bound dehydrogenases in G. oxydans 621H than expected and that the deletion of all of them is not lethal for the organism.  相似文献   

9.
Summary Gluconobacter oxydans subsp. suboxydans ATCC 621 oxidizes d-xylose to xylonic acid very efficiently, although it cannot grow on xylose as sole carbon source. The oxidation of xylose was found to be catalyzed by a membrane-bound xylose dehydrogenase. The xylono--lactone formed in the oxidation reaction is subsequently hydrolyzed to xylonic acid by a -lactonase. The complete oxidation pathway of d-xylose in G. oxydans is evidently located in the periplasmic space.  相似文献   

10.
A bacterium isolated from patulin-contaminated apples was capable of degrading patulin to a less-toxic compound, ascladiol. The bacterium was identified as Gluconobacter oxydans by 16S rRNA gene sequencing, whereas ascladiol was identified by liquid chromatography-tandem mass spectrometry and proton and carbon nuclear magnetic resonance. Degradation of up to 96% of patulin was observed in apple juices containing up to 800 μg/ml of patulin and incubated with G. oxydans.  相似文献   

11.
Certain strains of Gluconobacter oxydans have been known since the 1940s to produce the enzyme dextran dextrinase (DDase; EC2.4.1.2)—a transglucosidase converting maltodextrins into (oligo)dextran. The enzyme catalyses the transfer of an α1,4 linked glucosyl unit from a donor to an acceptor molecule, forming an α1,6 linkage: consecutive glucosyl transfers result in the formation of high molecular weight dextran from maltodextrins. In the early 1990s, the group of K. Yamamoto in Japan revived research on DDase, focussing on the purification and characterisation of the intracellular DDase produced by G. oxydans ATCC 11894. More recently, this was taken further by Y. Suzuki and coworkers, who investigated the properties and kinetics of the extracellular DDase formed by the same strain. Our group further elaborated on fermentation processes to optimise DDase production and dextran formation, DDase characterisation and its use as a biocatalyst, and the physiological link between intracellular and extracellular DDase. Here, we present a condensed overview of the current scientific status and the application potential of G. oxydans DDase and its products, (oligo)dextrans. The production of DDase as well as of dextran is first described via optimised fermentation processes. Specific assays for measuring DDase activity are also outlined. The general characteristics, substrate specificity, and mode of action of DDase as a transglucosidase are described in detail. Two forms of DDase are produced by G. oxydans depending on nutritional fermentation conditions: an intracellular and an extracellular form. The relationship between the two enzyme forms is also discussed. Furthermore, applications of DDase, e.g. production of (oligo)dextran, transglucosylated products and speciality oligosaccharides, are summarized.  相似文献   

12.
Quinoprotein quinate dehydrogenase (QDH) is a membrane-bound enzyme containing pyrroloquinoline quinone (PQQ) as the prosthetic group. QDH in Gluconobacter oxydans IFO3244 was found to be inducible by quinate and it is not constitutively expressed in the absence of quinate. The purification of holo-form of QDH to nearly homogeneity was achieved. The purified QDH appears to have two subunits of approximately 65 and 21 kDa, which could be the result of proteolysis of single polypeptide. Kinetic analysis indicated that the purified enzyme is much more specific to quinate than QDH from Acinetobacter calcoaceticus. The efficiency of the artificial electron acceptor was also determined.  相似文献   

13.
Summary The inhibitory effects of glycerol on Gluconobacter oxydans were measured separately. The kinetics of oxygen uptake rate representing the DHA production, the CO2 evolution rate representing the assimilation of the product, and the specific growth rate were mathematically modelled. Glycerol does not inhibit DHA formation and CO2-evolution.now: Institut für Biotechnologie, TU Graz, Petersgasse 12, 8010 Graz, Austria  相似文献   

14.
氧化葡萄糖酸杆菌酶学和分子生物学研究   总被引:1,自引:0,他引:1  
对氧化葡萄糖酸杆菌初级代谢途径中的关键酶及分子生物学研究做了系统的评述 ,展望了分子技术改造氧化葡萄糖酸杆菌和优化 2 KGA代谢途径的可能。  相似文献   

15.

Acetic acid bacteria are used in biotechnology due to their ability to incompletely oxidize a great variety of carbohydrates, alcohols, and related compounds in a regio- and stereo-selective manner. These reactions are catalyzed by membrane-bound dehydrogenases (mDHs), often with a broad substrate spectrum. In this study, the promoters of six mDHs of Gluconobacter oxydans 621H were characterized. The constitutive promoter of the alcohol dehydrogenase and the glucose-repressed promoter of the inositol dehydrogenase were used to construct a shuttle vector system for the fully functional expression of mDHs in the multi-deletion strain G. oxydans BP.9 that lacks its mDHs. This system was used to express each mDH of G. oxydans 621H, in order to individually characterize the substrates, they oxidize. From 55 tested compounds, the alcohol dehydrogenase oxidized 30 substrates and the polyol dehydrogenase 25. The substrate spectrum of alcohol dehydrogenase overlapped largely with the aldehyde dehydrogenase and partially with polyol dehydrogenase. Thus, we were able to resolve the overlapping substrate spectra of the main mDHs of G. oxydans 621H. The described approach could also be used for the expression and detailed characterization of substrates used by mDHs from other acetic acid bacteria or a metagenome.

  相似文献   

16.
Summary Gluconobacter oxydans cells were immobilized in calcium alginate and the preparation was used for the oxidation of glycerol to dihydroxyacetone. The characterization was done according to the guidelines given by the Working Party on Immobilized Biocatalysts of the European Federation of Biotechnology. The pH optimum of the preparation was found to be 5.0 and the temperature optimum was 40°C. However, the operational stability was better at 30°C. The glycerol concentration required to obtain half the maximal reaction rate was about 5 mM for both immobilized and free cells. At low concentrations of glycerol and high concentrations of dihydroxyacetone a slight inhibition was noted. No loss of activity of the immobilized preparation was observed after storage for 68 days at +4°C. Investigation of the operational stability revealed a half-life of 5 days. Studies of the influence of particle size and cell densities as well as that of oxygen concentration revealed that the oxygen supply was the rate limiting step.  相似文献   

17.
氧化葡萄糖酸杆菌SCB329和苏云金芽孢杆菌SCB933是混合发酵产生维生素C前体2-KLG两株主要菌种,本文对氧化葡萄糖酸杆菌SCB329的纯培养,传代及纯小菌的保存及其对产酸的影响作了研究。  相似文献   

18.
Two different membrane-bound enzymes oxidizing D-sorbitol are found in Gluconobacter frateurii THD32: pyroloquinoline quinone-dependent glycerol dehydrogenase (PQQ-GLDH) and FAD-dependent D-sorbitol dehydrogenase (FAD-SLDH). In this study, FAD-SLDH appeared to be induced by L-sorbose. A mutant defective in both enzymes grew as well as the wild-type strain did, indicating that both enzymes are dispensable for growth on D-sorbitol. The strain defective in PQQ-GLDH exhibited delayed L-sorbose production, and lower accumulation of it, corresponding to decreased oxidase activity for D-sorbitol in spite of high D-sorbitol dehydrogenase activity, was observed. In the mutant strain defective in PQQ-GLDH, oxidase activity with D-sorbitol was much more resistant to cyanide, and the H(+)/O ratio was lower than in either the wild-type strain or the mutant strain defective in FAD-SLDH. These results suggest that PQQ-GLDH connects efficiently to cytochrome bo(3) terminal oxidase and that it plays a major role in L-sorbose production. On the other hand, FAD-SLDH linked preferably to the cyanide-insensitive terminal oxidase, CIO.  相似文献   

19.
20.
The genomes of four keto-acid-producing Gluconobacter oxydans strains (ATCC9937, IFO3293, IFO12258 and DSM2343) were analysed by pulse-field gel electrophoresis (PFGE). PFGE of undigested DNA allowed the detection of plasmids in the following strains: ATCC9937 (3 plasmids; 8, 27, 31 kb), IFO3293 (9 kb), DSM2343 (21 kb). The three plasmids in ATCC9937 showed no homology to each other or to plasmids in the other strains. Seventeen restriction enzymes were tested for use in PFGE analysis of the G. oxydans strains and XbaI was chosen for restriction fragment analysis of the genomes. Fairly good resolution of restriction fragments at all size ranges was achieved by using three different pulse–time programs. The genome sizes of the four strains were estimated to be between 2240 kb and 3787 kb. The XbaI restriction patterns of the four strains showed no similarities to each other. Ten random cosmid clones of ATCC9937 were used as hybridization probes against the four strains, but, with the exception of one clone, hybridization signals were only observed with ATCC9937 itself. These data show that the four strains are not closely related.  相似文献   

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