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Microbial extradiol dioxygenases have a great potential in bioremediation, but their structure is very sensitive to various environmental and chemical agents. Immobilization techniques make the enzyme properties’ improvement possible. This is the first report of the usage of κ-carrageenan as a matrix for the immobilization of catechol 2,3-dioxygenase. The storage stability of entrapped catechol 2,3-dioxygenase from Stenotrophomonas maltophilia KB2 in κ-carrageenan hydrogel at 4ºC was found up to 14 days, while the free enzyme lost its activity within 24 hours. The immobilization of dioxygenase decreased the optimum temperature by 10ºC, while both soluble and immobilized enzyme showed similar pH properties. The Km, Vmax, and Hill constant values for the immobilized enzyme were 0.17 μM, 106.68 mU, and 1.00, respectively. The immobilized catechol 2,3-dioxygenase showed higher activity against 3-methylcatechol, hydroquinone, and tetrachlorohydroquinone than the soluble enzyme. Immobilization of catechol 2,3-dioxygenase protected the enzyme from inhibition and enhanced its resistance to inactivation during catalysis.
Aerobic bacteria degrading endosulfan were isolated from contaminated sludge. One of the isolates, LD-6, was identified as Stenotrophomonas sp. The bacterium could utilize endosulfan as the sole source of carbon and sulfur. 100 mg/l endosulfan was completely degraded within 10 days, and endosulfan diol and endosulfan ether were detected as major metabolites with a slight decrease in culture pH. The results indicated that Stenotrophomonas. sp. LD-6 might degrade endosulfan by a non-oxidative pathway. Biodegradation of both isomers was relatively better at a temperature range of 25–35°C, with a maximum at 30°C. In addition, cell crude extract of strain LD-6 could metabolize endosulfan rapidly, and degradative enzymes were intracellular distributed and constitutively expressed. Besides, application of the strain was found to promote the removal of endosulfan in soil. This study might help with the future research in better understanding of the biodegradation.
Nowadays biodegradations of harmful xenobiotics seems to be the best and cheapest method of purification of the polluted environment. VOCs are represented by vinyl acetate, which is thought to be carcinogenic. The aim of these studies was to isolate and determine the susceptibility profile for vinyl acetate of bacterial strains. The source of microorganisms was soil sampled in the area of Synthos S.A. in Oświęcim, Poland. From among 41 isolates, 4 Gram-negative strains were chosen for further analyses. As the control, one laboratory strain of Pseudomonas fluorescens PCM 2123 from The Polish Collection of Microorganisms (Wrocław) was used. Simultaneously, a susceptibility profile to vinyl acetate was performed on Stenotrophomonas maltophilia KB2 strain, aromatic compounds’ degrader. Vinyl acetate used in concentration of 3,000 ppm inhibited growth of gram-positive bacteria, and 4,000 ppm was the lethal dose for microorganisms from mixed populations. A toxicity test showed susceptibility to vinyl acetate at concentrations of 2,000 ppm. Three weeks of pre-incubation with 400 ppm of vinyl acetate magnified the level of sensitivity to 3,000 ppm of vinyl acetate for almost all strains. Although decomposition of vinyl acetate was observed even in the presence of 4,000, 5,000 and 6,000 ppm of vinyl acetate, growth was not observed. It was due to enlarged concentration of acetaldehyde, a product of hydrolysis ester bond of vinyl acetate.
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