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

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.


Heterotrophic nitrification profile as a function of time. Error bars represent deviations
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4697911&req=5

Fig3: Heterotrophic nitrification profile as a function of time. Error bars represent deviations

Mentions: The degradation of free cyanide resulted in the accumulation of ammonium in the medium, which suggested a possible hydrolytic mechanism of cyanide degradation (Ebbs 2004; Akcil et al. 2003). The maximum ammonium nitrogen concentration from the cultures that had an initial cyanide concentration of 250 and 450 mg CN−/L was 86 and 61 mg NH4+-N/L, respectively. Subsequently, the nitrate nitrogen concentration accumulated in the media, with an observed maximum nitrate nitrogen concentration of 31.2 and 62.4 mg NO3−-N/L being observed, respectively (see Fig. 2). The ammonium nitrogen concentration decreased after 64 and 41 h from both cultures, with the residual ammonium nitrogen concentration being 42 and 4.5 mg NH4+-N/L from the cultures that contained an initial cyanide concentration of 250 and 450 mg CN−/L, respectively. This showed heterotrophic nitrification capability of Pseudomonas aeruginosa STK 03. However, the organism was unable to remove nitrates, thus demonstrating the incapability of the organism to carry out aerobic denitrification. However, Pseudomonas stutzeri C3 was found to be able to carry out aerobic denitrification but was unable to carry out heterotrophic nitrification (Ji et al. 2015), while in a separate study Pseudomonas stutzeri YZN-001 was able to carry out nitrification and aerobic denitrification (Zhang et al. 2011); a suggestion that isolate STK 03 does not possess denitrification characteristics that are responsible for total nitrogen removal in cyanide-contaminated effluent. To prove heterotrophic nitrification and aerobic denitrification, both ammonium (as NH4Cl) and nitrate (as NaNO3) were used as nitrogen sources, in separate studies. STK 03 was able to carry out nitrification (see Fig. 3), achieving a nitrification rate of 1.56 mg NH4+-N L−1 h−1 with subsequent production and accumulation of nitrates and nitrites while ammonium stripping was determined to amount to 15 %. Both nitrates and nitrites increased during the nitrification stage; however, the concentration of nitrites decreased to 1.75 mg NO2−-N/L after 150 h, with the accumulation of nitrates being observed (Table 1).Fig. 2


Free cyanide and thiocyanate biodegradation by Pseudomonas aeruginosa STK 03 capable of heterotrophic nitrification under alkaline conditions
Heterotrophic nitrification profile as a function of time. Error bars represent deviations
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig3: Heterotrophic nitrification profile as a function of time. Error bars represent deviations
Mentions: The degradation of free cyanide resulted in the accumulation of ammonium in the medium, which suggested a possible hydrolytic mechanism of cyanide degradation (Ebbs 2004; Akcil et al. 2003). The maximum ammonium nitrogen concentration from the cultures that had an initial cyanide concentration of 250 and 450 mg CN−/L was 86 and 61 mg NH4+-N/L, respectively. Subsequently, the nitrate nitrogen concentration accumulated in the media, with an observed maximum nitrate nitrogen concentration of 31.2 and 62.4 mg NO3−-N/L being observed, respectively (see Fig. 2). The ammonium nitrogen concentration decreased after 64 and 41 h from both cultures, with the residual ammonium nitrogen concentration being 42 and 4.5 mg NH4+-N/L from the cultures that contained an initial cyanide concentration of 250 and 450 mg CN−/L, respectively. This showed heterotrophic nitrification capability of Pseudomonas aeruginosa STK 03. However, the organism was unable to remove nitrates, thus demonstrating the incapability of the organism to carry out aerobic denitrification. However, Pseudomonas stutzeri C3 was found to be able to carry out aerobic denitrification but was unable to carry out heterotrophic nitrification (Ji et al. 2015), while in a separate study Pseudomonas stutzeri YZN-001 was able to carry out nitrification and aerobic denitrification (Zhang et al. 2011); a suggestion that isolate STK 03 does not possess denitrification characteristics that are responsible for total nitrogen removal in cyanide-contaminated effluent. To prove heterotrophic nitrification and aerobic denitrification, both ammonium (as NH4Cl) and nitrate (as NaNO3) were used as nitrogen sources, in separate studies. STK 03 was able to carry out nitrification (see Fig. 3), achieving a nitrification rate of 1.56 mg NH4+-N L−1 h−1 with subsequent production and accumulation of nitrates and nitrites while ammonium stripping was determined to amount to 15 %. Both nitrates and nitrites increased during the nitrification stage; however, the concentration of nitrites decreased to 1.75 mg NO2−-N/L after 150 h, with the accumulation of nitrates being observed (Table 1).Fig. 2

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.