Klebsiella oxytoca, isolated from cyanide-containing wastewater, was able to utilize many nitriles as sole source of nitrogen. The major objective of this study was to explore the ability of K. oxytoca to utilize some nitriles and then further evaluate the pathways of transformation of cyanide compounds by K. oxytoca. Results from this study indicate that succinonitrile and valeronitrile were the most optimal sources of nitrogen for the growth of K. oxytoca. The biodegradation of acetonitrile proceeded with the formation of acetamide followed by acetic acid. The production of ammonia was also detected in this biodegradation experiment. Similar results were observed in the propionitrile biodegradation experiments. Collectively, this study suggests that the breakdown of acetonitrile or propionitrile by this bacterium was via a two-step enzymatic hydrolysis with amides as the intermediates and organic acids plus with ammonia as the end products.

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The dioxin-degrading bacterium strain NSYSU (NSYSU strain) has been isolated from dioxin-contaminated soil by selective enrichment techniques. In the present study, the NSYSU strain was investigated for its capability to biodegrade polychlorinated dibenzo--dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) under aerobic and anaerobic conditions. High-resolution gas chromatography-mass spectrometry and a chemically activated luciferase gene expression bioassay were performed to determine the presence of dioxin compounds. The results indicate that the NSYSU strain could degrade PCDDs and PCDFs under anaerobic conditions in liquid cultures. The main intermediates of the dechlorination process were identified. The results of the bioreactor test indicate that the NSYSU strain could also degrade PCDDs and PCDFs effectively in soil slurries under aerobic conditions. Results from the bioreactor experiment show that approximately 98 and 97% of octachlorodibenzofuran and OCDD were degraded, respectively. The dioxin concentrations in soil slurry decreased from 5823 to 1198 pg toxic equivalency g, resulting in total dioxin removal of 79%. These first findings suggest that the NSYSU strain has the potential to be an effective tool for the bioremediation of soils contaminated with highly recalcitrant organic compounds.

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