A. M. Bezborodov

Organization of metabolic pathways and molecular-genetic mechanisms of xenobiotic degradation in microorganisms: A review

Contemporary data on the mechanism of biodegradation of aromatic hydrocarbons and biodegradation genes (genomic organization and pathways of evolution) in diverse groups of microorganisms have been reviewed. Studies of this problem are topical, in view of the need in identification and construction of new strains degrading xenobiotics, particularly those halogenated. For this reason, emphasis is placed on specific features of explored metabolic pathways that can be used for constructing new enzymatic systems not present in nature. Sections on the mechanisms of genomic rearrangements involving biodegradation determinants are presented from the same standpoint. Part of the review is devoted to analyzing methods used for studying the population dynamics of bacterial communities involved in xenobiotic degradation in natural biotopes or industrial waste disposal plants. Particular attention is given to methods of gene systematics.

Monitoring of microbial degraders in manned space stations

Samples of microorganisms from the surface of constructions of Mir Space Station (Mir SS) were taken and examined after 13 years of operation. The following microorganisms were isolated and identified: 12 fungal species belonging to the genera Penicillium, Aspergillus, Cladosporium, and Aureobasidium; 3 yeast species belonging to the genera Debaryomyces, Candida, and Rhodotorula; and 4 bacterial species belonging to the genera Bacillus, Myxococcus, and Rhodococcus. The predominant species in all samples was Penicillium chrisogenum. It was shown that the fungi isolated could damage polymers and induce corrosion of aluminum-magnesium alloys. We commenced a study of microbial degraders on constructions of the Russian section of the International Space Station (RS ISS). Twenty-six species of fungi, bacteria, yeasts, and actinomycetes, known as active biodegraders, were identified in three sample sets taken at intervals. We founded a collection of microorganisms surviving throughout space flights. This collection can be used to test spacecraft production materials, in order to determine their resistance to biodegradation.

Lipases in catalytic reactions of organic chemistry

Aspects of enzymatic catalysis in lipase-catalyzed reactions of organic synthesis are discussed in the review. The data on modern methods of protein engineering and enzyme modification allowing a broader range of used substrates are briefly summarized. The application of lipase in the preparation of pharmaceuticals and agrochemicals containing no inactive enantiomers and in the synthesis of secondary alcohol enantiomers and optically active amides is demonstrated. The subject of lipase involvement in the C-C bond formation in the Michael reaction is discussed. Data on the enzymatic synthesis of construction materials—polyesters, siloxanes, etc.—are presented. Examples demonstrating the application of lipase enzymatic catalysis in industry are given.

Ethylene-Induced Activation of Xylanase in Adventitious Roots of Maize as a Response to the Stress Effect of Root Submersion

Submersion of roots of ten-day-old maize (Zea maysL.) seedlings was accompanied by a decrease in pO2and an increase in pCO2of the medium adjacent to the roots. These changes stimulated ethylene evolution in intact plants. Enhanced biosynthesis of ethylene was accompanied by xylanase activation in adventitious roots. As a result, an enhanced formation of aerenchyma was observed in the cortex of adventitious roots. Therefore, these processes resulted in the development of a ventilation system by which O2can reach the root system exposed to hypoxia. The volume of aerenchyma was assessed by the volume of gas cavities (porosity). In contrast to the main root, the growth of adventitious roots was not inhibited under these conditions. Enlargement of the stem base and increase in the number of aerenchymatous adventitious roots facilitated the oxygen supply to the submerged organs of the plants.

Enzymatic biocatalysis in chemical synthesis of pharmaceuticals (Review)

In this review we summarize the available research on enzymatic biocatalysis in the chemical synthesis of drugs. We focus on oxydoreductsases, particularly ketoreductases, that are widely used in biotechnological processes: alpha- and omega-transaminases, lipases, nitrile hydrolases, and aldolases. The potential for the extended use of novel enzymes produced via bioengineering is discussed.

Nanobiotechnology and biosensor research

Nanobiotechnology is defined as an interdisciplinary field of science that studies the application of fine-sized biological objects (of nanoscale, 1–100 nm) to design the devices and systems of the same size that utilize for new purposes the unusual, known, or previously unknown effects. Analysis demonstrates that the final goals, approaches, solution methods, and applications of nanostructures and biological sensors have much in common. This brief review attempts to systematize a number of the available data and pick out an organic connection of the new research direction with the field of biosensor technology, which have reached the level of sustainable development.

Assimilation of Propane and Characterization of Propane Monooxygenase from Rhodococcus erythropolis3/89

The ability of propane-assimilating microorganisms of the genus Rhodococcusto utilize metabolites of the terminal and subterminal pathways of propane oxidation was studied. Propane monooxygenase of Rhodococcus erythropolis3/89 was shown to be an inducible enzyme catalyzing epoxidation and hydroxylation of organic compounds. The optimum conditions for the epoxidation of gaseous and liquid alkenes and the hydroxylation of aromatic carbohydrates were found.

Oxidation of organic compounds by propane monooxygenase ofRhodococcus erythropolis 3/89

The ability of propane monooxygenase ofRhodococcus erythropolis 3/89 to catalyze oxidation of higher liquid alkenes and aromatic hydrocarbons was studied. Optimal conditions of tetradecene epoxidation and benzene hydroxylation were found. Under these conditions, oxidation was shown to be accompanied by a 100% conversion of benzene to phenol.

Isolation and purification of acetolactate synthase and acetolactate decarboxylase from the culture ofLactococcus lactis

Enzymes catalyzing the synthesis and subsequent transformation of α-acetolactate (AcL)—acetolactate synthase (AcLS) and acetolactate decarboxylase (AcLDC)—were isolated and partially purified from the cells of lactic acid bacteriaLactococcus lactis ssp.lactis biovar.diacetylactis, strain 4. The preparation of AcLS, purified 560-fold, had a specific activity of 358 300 U/mg protein (9% yield). The preparation of AcLDC., purified 4828-fold, had a specific activity of 140 U/mg protein (4.8% yield). The enzymes exhibited optimum activity at pH 6.5 and 6.0, respectively (medium, phosphate buffer). The values of apparentKm, determined for AcLS and AcLDC with pyruvate and AcL, respectively, were equal to 70 mM and 20 mM. AcLS appeared as an allosteric enzyme with low affinity for the substrate and a sigmoid dependence of the activity on the substrate concentration. In the case of AcLDC, this dependence was hyperbolic and the affinity of the enzyme for its substrate was high (Km = 20 mM). Leucine, valine, and isoleucine were shown to be activators of AcDLC.

Purification and Characterization of endo-(1→4)-β-xylanase fromGeotrichum candidum 3C

A method of purification of endo-( 1 → 4)-β-xylanase (endoxylanase; EC 3.2.1.8) from the culture liquid ofGeotrichum candidum 3C, grown for three days, is described. The enzyme, purified 23-fold, had a specific activity of 32.6 U per mg protein (yield, 14.4%). Endoxylanase was shown to be homogeneous by SDS-PAGE (molecular weight, 60 to 67 kDa). With carboxymethyl xylan as the substrate, the optimum activity (determined viscosimetrically) was recorded at pH 4.0 (pI 3.4). The enzyme retained stability at pH 3.0-4.5 and 30–45°C for 1 h. With xylan from birch wood, the hydrolytic activity of the enzyme (ability to saccharify the substrate) was maximum at 50°C. In 72 h of exposure to 0.2 mg/ml endoxylanase, the extent of saccharification of xylans from birch wood, rye grain, and wheat straw amounted to 10,12, and 7.7%, respectively. At 0.4 mg/ml, the extent of saccharification of birch wood xylan was as high as 20%. In the case of birch wood xylan, the initial hydrolysis products were xylooligosaccharides with degrees of polymerization in excess of four; the end products were represented by xylobiose, xylotriose, xylose, and acid xylooligosaccharides.