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Free cyanide and thiocyanate biodegradation by Pseudomonas aeruginosa STK 03 capable of heterotrophic nitrification under alkaline conditions

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ABSTRACT

An alkali-tolerant bacterium, Pseudomonas aeruginosa STK 03 (accession number KR011154), isolated from an oil spill site, was evaluated for the biodegradation of free cyanide and thiocyanate under alkaline conditions. The organism had a free cyanide degradation efficiency of 80 and 32 % from an initial concentration of 250 and 450 mg CN−/L, respectively. Additionally, the organism was able to degrade thiocyanate, achieving a degradation efficiency of 78 and 98 % from non- and free cyanide spiked cultures, respectively. The organism was capable of heterotrophic nitrification but was unable to denitrify aerobically. The organism was unable to degrade free cyanide in the absence of a carbon source, but it was able to degrade thiocyanate heterotrophically, achieving a degradation efficiency of 79 % from an initial concentration of 250 mg SCN−/L. Further increases in thiocyanate degradation efficiency were only observed when the cultures were spiked with free cyanide (50 mg CN−/L), achieving a degradation efficiency of 98 % from an initial concentration of 250 mg SCN−/L. This is the first study to report free cyanide and thiocyanate degradation by Pseudomonas aeruginosa. The higher free cyanide and thiocyanate tolerance of the isolate STK 03, which surpasses the stipulated tolerance threshold of 200 mg CN−/L for most organisms, could be valuable in microbial consortia for the degradation of cyanides in an industrial setting.

No MeSH data available.


Thiocyanate degradation profile and formation of degradation products with the presence of free cyanide. Error bars represent deviations. The arrows represent cyanide spiking intervals
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Fig6: Thiocyanate degradation profile and formation of degradation products with the presence of free cyanide. Error bars represent deviations. The arrows represent cyanide spiking intervals

Mentions: Thiocyanate degradation under the influence of free cyanide spiking was also evaluated (Fig. 6). Cyanide spiking was carried out at 25 and 100 h. Under these conditions, STK 03 had a degradation efficiency increase to 98 % from an initial concentration of 250 mg SCN−/L, meaning that the presence of free cyanide propagated thiocyanate degradation. It was hypothesised that this observation might be due to a metabolic shock response that might have triggered or upregulated the expression of thiocyanate degrading enzymes. The residual thiocyanate concentration was found to be 4.7 mg SCN−/L. Sulphates and nitrates accumulated throughout the experiments reached a maximum sulphate and nitrate concentration of 144.5 mg SO42−-S/L and 55 mg NO3−-N/L. Thiocyanate degradation was accompanied by ammonium generation, resulting in a maximum ammonium concentration of 123 mg NH4+-N/L. Ammonium oxidation from 120 h was observed with a sudden increase in nitrates thereafter, although denitrification was not observed.Fig. 6


Free cyanide and thiocyanate biodegradation by Pseudomonas aeruginosa STK 03 capable of heterotrophic nitrification under alkaline conditions
Thiocyanate degradation profile and formation of degradation products with the presence of free cyanide. Error bars represent deviations. The arrows represent cyanide spiking intervals
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697911&req=5

Fig6: Thiocyanate degradation profile and formation of degradation products with the presence of free cyanide. Error bars represent deviations. The arrows represent cyanide spiking intervals
Mentions: Thiocyanate degradation under the influence of free cyanide spiking was also evaluated (Fig. 6). Cyanide spiking was carried out at 25 and 100 h. Under these conditions, STK 03 had a degradation efficiency increase to 98 % from an initial concentration of 250 mg SCN−/L, meaning that the presence of free cyanide propagated thiocyanate degradation. It was hypothesised that this observation might be due to a metabolic shock response that might have triggered or upregulated the expression of thiocyanate degrading enzymes. The residual thiocyanate concentration was found to be 4.7 mg SCN−/L. Sulphates and nitrates accumulated throughout the experiments reached a maximum sulphate and nitrate concentration of 144.5 mg SO42−-S/L and 55 mg NO3−-N/L. Thiocyanate degradation was accompanied by ammonium generation, resulting in a maximum ammonium concentration of 123 mg NH4+-N/L. Ammonium oxidation from 120 h was observed with a sudden increase in nitrates thereafter, although denitrification was not observed.Fig. 6

View Article: PubMed Central - PubMed

ABSTRACT

An alkali-tolerant bacterium, Pseudomonas aeruginosa STK 03 (accession number KR011154), isolated from an oil spill site, was evaluated for the biodegradation of free cyanide and thiocyanate under alkaline conditions. The organism had a free cyanide degradation efficiency of 80 and 32 % from an initial concentration of 250 and 450 mg CN−/L, respectively. Additionally, the organism was able to degrade thiocyanate, achieving a degradation efficiency of 78 and 98 % from non- and free cyanide spiked cultures, respectively. The organism was capable of heterotrophic nitrification but was unable to denitrify aerobically. The organism was unable to degrade free cyanide in the absence of a carbon source, but it was able to degrade thiocyanate heterotrophically, achieving a degradation efficiency of 79 % from an initial concentration of 250 mg SCN−/L. Further increases in thiocyanate degradation efficiency were only observed when the cultures were spiked with free cyanide (50 mg CN−/L), achieving a degradation efficiency of 98 % from an initial concentration of 250 mg SCN−/L. This is the first study to report free cyanide and thiocyanate degradation by Pseudomonas aeruginosa. The higher free cyanide and thiocyanate tolerance of the isolate STK 03, which surpasses the stipulated tolerance threshold of 200 mg CN−/L for most organisms, could be valuable in microbial consortia for the degradation of cyanides in an industrial setting.

No MeSH data available.