Nitrile degradation by free and immobilized cells of the thermophile Bacillus sp. UG-5B, isolated from polluted industrial waters |
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Authors: | Ludmila Kabaivanova Plamen Dimitrov Ivanka Boyadzhieva Stefan Engibarov Elena Dobreva Elka Emanuilova |
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Institution: | (1) Department of Extremophilic Bacteria, Institute of Microbiology, Bulgarian Academy of Sciences, “Acad. G. Bonchev” Street 26, 1113 Sofia, Bulgaria |
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Abstract: | A moderately thermophilic Gram-positive, sporulating, rod-shaped strain of Bacillus with nitrile-degrading activity was isolated from polluted industrial waters. Whole cells and cell-free extracts from the
end of exponential growth phase expressed 7.6 nkat mg−1 and 2.0 nkat mg−1 benzonitrile-degrading activity, respectively, after cultivation in a fermentor with complex medium containing benzonitrile
as an inducer. The benzonitrile degradation took place via the nitrilase pathway directly to benzoic acid without intermediate
formation of benzamide. Samples with benzonitrilase activity of 7.6 nkat mg−1 converted 3 mg benzonitrile in 1 h at 45°C. The half-life of benzonitrilase activity for a whole cell suspension and for
cells immobilized in 2% agar was 4.5 min and 6 min at 70°C without substrate and 3 min at 90°C with substrate, respectively.
The nitrilase had a broad substrate spectrum. The active biocatalyst obtained by immobilization was used in a continuous process
and total biodegradation of 14.1 mM benzonitrile and 37.2 mM 4-cyanopyridine in a column bioreactor at 50°C for 5 h was achieved. |
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Keywords: | Bacillus Biodegradation Immobilization Nitrilase Thermostability |
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