Asymmetric oxidation by Gluconobacter oxydans

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.     

Ketogluconate formation by Gluconobacter species

Summary When G. oxydans ATCC 621-H was grown in batch culture in a complex medium with glucose, ketogluconates were produced when the pH in the culture was maintained at 5.5. Without pH control gluconate was the only product of glucose oxidation, but at pH 5.5 the gluconate so produced was further oxidized to ketogluconates. Production of ketogluconates started when glucose was almost completely exhausted. It was shown that the actual glucose and gluconate concentrations in the culture do not determine the onset of ketogluconate formation during growth. Both 2 and 5 ketogluconate were produced. Addition of CaCO₃ to the medium favored the production of 5 ketogluconate. However, under these conditions minor quantities of 2 ketogluconate were also formed. The sequential production of gluconate and ketogluconates from glucose was not only restricted to G. oxydans ATCC 621-H. A number of G. oxydans strains when grown under standard conditions in a pH controlled batch culture, all produced ketogluconates from glucose via an intermediate accumulation of gluconate. Although the ratios of the ketogluconates produced varied from strain to strain, all strains produced both 2 and 5 ketogluconate.     

Dextran dextrinase and dextran of Gluconobacter oxydans

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.     

The genus Gluconobacter and its applications in biotechnology

Organisms of the genus Gluconobacter have been widely utilized within the biotechnology industry for many decades, due to their unique metabolic characteristics. The metabolic features that render Gluconobacter so useful in biotransformation processes, vitamin synthesis, and, as the biological element in sensor systems, are critically evaluated, and the relevance of recent biochemical genetic studies to current and future industrial Gluconobacter processes is discussed. The impact of recombinant gene technology on the status of Gluconobacter processes and the potential use of such techniques in clarifying aspects of the physiology of Gluconobacter is reviewed.     

Gluconobacter oxydans: its biotechnological applications

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.     

Biotransformation of patulin by Gluconobacter oxydans

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.     

Phospholipid Composition of Gluconobacter cerinus

Phospholipids of Gluconobacter cerinus were investigated. The cells of this bacterium were found to have cardiolipin, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine together with three ornithine-containing lipids. Phosphatidylcholine was the most abundant of these phospholipids, and calculated at 31.0% of total phospholipids in the cells at the late logarithmic phase. The fatty acid of this lipid was composed of palmitate, stearate and vaccenate, and there were no remarkable differences in quality among fatty acids of these four phospholipids. The phosphatidylcholine was also found in other acetic acid bacteria.     

葡糖杆菌属分类及其主要应用的研究进展

葡糖杆菌是醋酸菌科的一个重要属,与人类关系密切,该属中部分菌株在维生素C、米格列醇的工业生产及合成中起着重要作用;此外,该属菌株还能氧化葡萄糖生成葡糖酸盐和酮基葡糖酸等工业重要中间体。综述了葡糖杆菌的研究进展,主要介绍了葡糖杆菌的生理生化特征、分类进展及其主要应用,可以为广大醋酸菌研究者提供参考。     

氧化葡萄糖酸杆菌酶学和分子生物学研究

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。     

Oxidative d-xylose metabolism of Gluconobacter oxydans

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.     

Biotransformation of Patulin by Gluconobacter oxydans

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.     

Glucose oxidation and PQQ-dependent dehydrogenases in Gluconobacter oxydans

Gluconobacter oxydans is famous for its rapid and incomplete oxidation of a wide range of sugars and sugar alcohols. The organism is known for its efficient oxidation of D-glucose to D-gluconate, which can be further oxidized to two different keto-D-gluconates, 2-keto-D-gluconate and 5-keto-D-gluconate, as well as 2,5-di-keto-D-gluconate. For this oxidation chain and for further oxidation reactions, G. oxydans possesses a high number of membrane-bound dehydrogenases. In this review, we focus on the dehydrogenases involved in D-glucose oxidation and the products formed during this process. As some of the involved dehydrogenases contain pyrroloquinoline quinone (PQQ) as a cofactor, also PQQ synthesis is reviewed. Finally, we will give an overview of further PQQ-dependent dehydrogenases and discuss their functions in G. oxydans ATCC 621H (DSM 2343).     

Occurrence of Phosphatidylcholine in Gluconobacter cerinus

Phosphatidylcholine was associated with soybean protein in two types of interaction. One is due to hydrophobic interaction between a phosphatidylcholine molecule and hydrophobic regions of the protein. The other is due to the binding of phosphatidylcholine lamellae to the protein surface.     

Purification and properties of dihydroxyacetone kinase from Gluconobacter suboxydans

Different carbon and nitrogen sources had little effect on the level of dihydroxyacetone kinase formed in the cells of Gluconobacter suboxydans. The enzyme was purified to homogeneity from cell-free extract of the organism by ammonium sulfate fractionation and chromatographies on DEAE-cellulose, hydroxyapatite and Sephadex G-200 (60-fold purification, 6% yield). Its molecular weight was 260,000; it was stabilized by addition of ATP, dithiothreitol, 2-mercaptoethanol or EDTA, and it reacted optimally at pH 6.5. d-Glyceraldehyde was equally as effective as DHA as a phosphate acceptor (K_m: 0.30 mM each). UTP showed 15% of the reactivity of ATP as a phosphate donor. K_m values for ATP were 0.33 mM in phosphorylation of dihydroxyacetone and 0.39 mM with d-glyceraldehyde. The enzyme activity was dependent on Mg²⁺ but not on Mn²⁺. The reaction with dihydroxyacetone as an acceptor was inhibited by d-glyceraldehyde. The inhibition was competitive with respect to dihydroxyacetone 3K_i=0.09 mM) and noncompetitive with respective to ATP (K_i=5.7 mM).     

Inhibitory effects of glycerol on Gluconobacter oxydans

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     

氧化葡萄糖酸杆菌SCB329的培养及保存

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。     

Intergeneric protoplast fusion between Gluconobacter oxydans and Corynebacterium species.

Intergeneric protoplast fusion between 2,5-diketo-gluconic acid producing Gluconobacter oxydans (ATCC 9937) and a mutant strain of Corynebacterium species (ATCC 31090), capable of reducing 2,5-diketo-gluconic acid to 2-keto-L-gulonic acid, a penultimate step in vitamin C production) resulted in viable recombinants. Some of the fusion products exhibited the capacity to convert D-glucose to 2-keto-L-gulonic acid, but the conversion rate is low.     

Acetate production from lactate and glucose fermentation by Gluconobacter oxydans

Summary The production of acetate from the fermentation of lactate by Gluconobacter oxydans was studied. Batch experiments showed that glucose was the preferred substrate compared to lactate. A fed-batch culture was fed with a mixture of glucose and lactate followed by periodic addition of lactate. The maximum productivity of acetate was 0.16 g/l h but this value decreased during the fedbatch culture due to growth inhibition by acetate.     

Oxidation of trans- and cis-1,2-cyclohexanediol by Gluconobacter oxydans

Summary The enzymatic oxidation of 1,2-cyclohexanediol and related substrates by Gluconobacter oxydans (ATCC 621) was investigated. At low pH, membrane-bound enzymes were active and at high pH, NAD-dependent, soluble enzymes showed activity. Whole bacterial cells were used to catalyze some bioconversions. Racemic trans-1,2-cyclohexanediol was oxidized at pH 3.5 to give (R)-2-hydroxycyclohexanone (96% e.e.) and at pH 8.0 the same substrate was oxidized to (S)-2-hydroxycyclohexanone (97% e.e.). The latter conversion was severely inhibited by the reaction product while the former was not significantly product inhibited. (S)-2-hydroxycyclohexanone (97% e.e.) was also prepared from cis-1,2-cyclohexanediol by oxidation with G. oxydans cells at pH 3.5 in a reaction which continued to 100% conversion.     

Gluconobacter oxydans NH-10中短链D-阿拉伯糖醇脱氢酶的研究

以氧化葡萄糖酸杆菌(Gluconobacter oxydans)NH-10基因组DNA为模板,扩增得到D-阿拉伯糖醇脱氢酶基因arDH,将其克隆到大肠杆菌表达载体JM109(DE3)中进行诱导表达。SDS-PAGE电泳分析ArDH的分子量约为30 kDa,是一个短链脱氢酶,既能催化D-阿拉伯糖醇氧化为D-木酮糖,又能催化D-木酮糖还原为D-阿拉伯糖醇。催化氧化反应时,对D-阿拉伯糖醇的K_m为60.67 mmol/L,V_max为0.803 U/mg;它能同时依赖于NAD⁺和NADP⁺,但是更加偏好辅酶NAD⁺;最适pH为12.0。还原反应对D-木酮糖的 K_m为36.39 mmol/L,V_max为1.71 U/mg;最优pH为7.0,最适温度均为30℃。