Thiocyanate Degradation by Pure and Mixed Bacterial Cultures

Patil Yogesh B (2008) Thiocyanate degradation by pure and mixed bacterial cultures. Bioinfolet 5(3): 308-309 (ISSN: 0973-1431)

2 Pages Posted: 16 Nov 2014

See all articles by Yogesh Patil

Yogesh Patil

Symbiosis International (Deemed University), Pune, India

Date Written: November 15, 2014

Abstract

Cyanide (CN) containing effluents are frequently generated from mining and electroplating industries. Since cyano-group of chemicals is extremely toxic, they may cause damages to biotic and abiotic components of the environment. Conventional treatment processes currently in use are associated with several problems. Therefore, biological treatment technologies are gaining importance as an effective alternative. Activated sludge process is usually used for the treatment of SCN containing effluents, wherein microorganisms degrade this substance as the sole source of nitrogen, sulphur and/or carbon and energy. Since biological treatment systems are limited to a very low concentration of CN, microbial degradation of SCN has been extensively studied in the recent times. The present paper report the results obtained on SCN degradation by pure and mixed bacterial cultures (consortium) isolated from garden soil and activated sludge.

To judge SCN degradation efficiency of isolated cultures, experiments were performed in Erlenmeyer flasks containing 100 ml sterile M-9 medium (pH 7.0). The M-9 medium contained Na2HPO4.2H2O - 3.0 g; KH2PO4 - 1.5 g; NaCl - 0.25 g; distilled water - 1000 ml (Millar, 1972); 1 ml/l trace metal solution (Bauchop and Elsden, 1960) and 50 mg/l (= 0.084 g) potassium thiocyanate (KSCN), which served as a nitrogen source. Glucose (10 mM = 1.8 g) was used as the carbon source. Cell suspension (0.1 ml) containing 108 cells/ml were inoculated into the flasks and were incubated at 30°C in a rotary shaker at 150 rpm for 48 h.

Experiments were performed in duplicates and repeated twice with appropriate controls. Residual SCN- levels were determined periodically as per the Standard Methods (APHA-AWWA-WEF, 1998). The SCN degradation efficiency of individual and mixed bacterial culture was expressed in terms of percent total SCN degraded in 48 h. Reaction rate and first order rate constants for SCN biodegradation were calculated using equations 1 and 2 respectively (Sellers, 1999). C / t = k C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eq. 1 ln Ct – ln Co = - k t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eq. 2 Where, C = concentration of SCN (mg/l); t=time (h); k=rate of reaction/first order rate constant (h.1); C°=initial SCN concentration (mg/l) and Ct =SCN concentration at time t.

There was wide variation in SCN degradation efficiency of the isolates (Table 1). Consortium of bacterial cultures isolated from garden soil and activated sludge degraded >99.9% SCN in 42 and 36 h giving the SCN degradation rate constant (k) of 0.0931 and 0.1086 per h, respectively; while Pseudomonas sp. SKB-2 degraded only 75.9% of SCN in 48 h (k=0.027 per h). Among the individual bacterial isolates, Pseudomonas sp. SKB-4 was found to be more efficient SCN- degrader. The data also show that the first order rate constants of bacterial consortiums were two to three folds higher than their individual isolates.

The main objective of the present experiment was to check the efficacy of bacterial cultures for SCN degradation. The results clearly showed that the bacterial consortium’s were highly efficient as compared to their respective individual isolates (Table 1); and this corroborate with the studies carried out by Patil and Paknikar (2000) on metal-cyanide biodegradation by bacterial consortium. The study also showed that bacterial consortium isolated from activated sludge was more efficient as compared to the consortium isolated from garden soil. Thus, the consortium isolated from activated sludge has future potential for its use in bioprocess for removal of SCN.

Suggested Citation

Patil, Yogesh, Thiocyanate Degradation by Pure and Mixed Bacterial Cultures (November 15, 2014). Patil Yogesh B (2008) Thiocyanate degradation by pure and mixed bacterial cultures. Bioinfolet 5(3): 308-309 (ISSN: 0973-1431). Available at SSRN: https://ssrn.com/abstract=2524815

Yogesh Patil (Contact Author)

Symbiosis International (Deemed University), Pune, India ( email )

Lavale (Hill top)
Gram: Lavale, Tal: Mulshi, Dist: Pune
Pune, Maharashtra 412115
India

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