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ABSTRACT: The aim of this work was to isolate oil-degrading bacteria that use chitin or keratin as carbon sources from oil contaminated soils; and additionally to study if oil removal by these bacteria is enhanced when a chitinous or a keratinous waste is added to the culture media. To isolate the above-mentioned bacteria, 12 soil samples were collected close to an oil-well. Such soils showed unsuitable nutrients content, but their counts of heterotrophic bacteria ranged within 10(5)-10(8) CFU g(-1) soil, of which 0.1-77% corresponded to oil hydrocarbon-degrading ones. By sampling on plates, 109 oil-degrading bacterial isolates were obtained. Their keratinase and chitinase activities were then screened by plate assays and spectrophotometric methods, resulting in 13 isolates that were used to integrate two mixed cultures, one keratinolytic and the other chitinolytic. These mixed cultures were grown in media with oil, or oil supplemented with chicken-feathers or shrimp wastes. The oil-hydrocarbon removal was measured by gas chromatography. Results showed that keratinolytic bacteria were better enzyme producers than the chitinolytic ones, and that oil removal in the presence of chicken-feathers was 3.8 times greater than with shrimp wastes, and almost twice, in comparison with oil-only added cultures. Identification of microorganisms from the mixed cultures by 16S rDNA, indicated the presence of seven different bacterial genera; Stenotrophomonas, Pseudomonas, Brevibacillus, Bacillus, Micrococcus, Lysobacter and Nocardiodes. These findings suggest that the isolated microorganisms and the chicken-feather wastes could be applied to the cleaning of oil-contaminated environments, whether in soil or water.
Environmental Technology 03/2008; 29(2):171-82. · 1.41 Impact Factor
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ABSTRACT: A simple and sensitive method based on the use of colloidal chitin stained with Remazol Brilliant Blue R (RBB) is proposed to evaluate chitinase activity. If this colloidal-stained substrate is included as a carbon source in a liquid medium, this technique allows the selection or the comparison of chitinolytic microorganisms. The colloidal substrate is proportionally solubilized and the dye released is spectrophotometrically quantified at 595 nm. The procedures used for the staining and fixing of RBB in the colloidal chitin, and a comparison with the commercial substrate chitin-azure, are presented. The influence of several physicochemical and enzymatic parameters on the release of dyes is also shown. Both stained substrates were used for studying the effect of pH, substrate concentration, temperature and time on the chitinase reaction of Bacillus thuringiensis Bt-107.
Journal of Microbiological Methods 03/2004; 56(2):213-9. · 2.09 Impact Factor
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ABSTRACT: The ability to produce extracellular chitosanase (EC 3.2.1.132) was found by plate assays in 18 (23%) out of 77 crystalliferous strains of Bacillus thuringiensis. The best chitosanase producer was selected after the growth chosen in a liquid medium with colloidal chitosan as carbon source. Enzyme production was optimized (a 4-d incubation at 32 degrees C with shaking in a medium of pH 6.5 with 4% colloidal chitosan) and the enzyme was partially characterized. This is the first report on the chitosanase of B. thuringiensis.
Folia Microbiologica 02/2004; 49(1):94-6. · 0.68 Impact Factor
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Bulletin of Environmental Contamination and Toxicology 01/2003; 69(6):835-42. · 1.02 Impact Factor
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Bulletin of Environmental Contamination and Toxicology 01/2002; 69(6):0835-0842. · 1.02 Impact Factor
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ABSTRACT: This paper reports the selection and characterization of Bacillus thuringiensis strains, with ability to grow in a proteo-chitinaceous substrate (milled shrimp waste) as the sole ingredient. Selected strains were able to produce crystal proteins, as well as proteases and chitinases as fermentation by-products. By a preliminary, qualitative screening of 152 B. thuringiensis strains, grown on media rich in protein and chitin, eight strains were selected. These strains were cultured in a liquid medium containing milled shrimp waste and their kinetics of protease production were followed. The two most active proteolytic strains (Bt-103 and Bt-112) were characterized by their crystal protein content, plasmid profiles, crystal ultrastructure, and toxicity towards Manduca sexta, Aedes aegypti and Leptinotarsa texana. The only activity recorded in these species was moderate toxicity of strain Bt-112 against Manduca sexta first instar larvae, as well as the highest proteolytic and chitinolytic activities. Its bipyramidal crystals were associated with semi-cuboidal inclusions and although its crystal proteins were similar to those of B. thuringiensis kurstaki (HD-1), its plasmid content was quite different. Serotyping of Bt-112 indicated that it belongs to serovar. tolworthi. Further studies with a similar strategy might render more strains with ability to grow in a rich waste by-product like the shrimp waste, which may show not only higher insecticidal activity, but also with the ability to produce extracellular enzymes with biotechnological applications.
World Journal of Microbiology and Biotechnology 03/1999; 15(2):299-308. · 1.53 Impact Factor
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ABSTRACT: The strain Bt-NGRA of Bacillus thuringiensis, isolated from a highly transformer oil contaminated soil, has the ability to produce high levels of extracellular caseinase, keratinase, elastase, lipase, phospholipase, esterase, and nuclease. Such a strain belongs to the serovar finitimus, and forms a bipyramidal crystal attached to the spore, constituted by a ca. 120 kDa protein, which has low insecticidal activity against Manduca sexta larvae (Lepidoptera), and none against Leptinotarsa texana (Coleoptera), Aedes aegypti and Culex quinquefasciatus (Diptera). Additionally, Bt-NGRA has only one plasmid (~43 MDa), produces no β-exotoxin and is able to grow in a medium with transformer oil as sole carbon source. When Bt-NGRA was cultured in presence of polychlorinated biphenyl mixture, some tetra, penta and hexachlorobiphenyls were partially degraded (33, 32 and 21%, respectively). This is the first report of a Bacillus thuringiensis strain isolated from a highly polychlorinated biphenyls contaminated soil.
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ABSTRACT: The aim of this work was to evaluate the effect of keratinous waste addition on oil-hydrocarbon removal, through a mixed culture of oil-degrading bacteria, with the ability to secrete keratinases. The mixed culture was grown in the media with oil, or oil supplemented with chicken-feathers as the keratinous waste. Residual oil-hydrocarbons were determined as total petroleum hydrocarbons (TPHs) and oil fractions and then quantified by GC–FID and GC–MS.Results showed that in presence of the keratinous waste, the removal of oil-hydrocarbons was 57,400 mg l−1, meanwhile the treatment without waste presented an oil-hydrocarbons removal of 35,600 mg l−1. The aliphatic fraction was the most removed in both treatments. In addition, chromatographic profiles indicated that the aliphatic fraction showed different degradation pattern; in the presence of keratinous wastes, the C18 to C28 compounds were preferably removed over the C10 to C17. The addition of keratinous waste not only improved the oil-hydrocarbons removal but, it changed the removal pattern of the target hydrocarbons.
International Biodeterioration & Biodegradation.
