Abstract
Remediation of cyanide contaminated water bodies using microorganisms is a popular alternative over chemical and physical methods of cyanide detoxification. The objective of the present study is to develop a microbial consortium using three bacteria, i.e., Enterobacter sp. RL2a, Serratia marcescencs RL2b and Achromobacter sp. RL2c for effective degradation of simulated cyanide wastewater. In vitro cyanide degradation was optimum with 2% inoculum volume of cells; pH 6.0, 30°C temperature at 20 mM substrate concentration leading to complete cyanide removal in 36 h. Response surface methodology (RSM) approach was used for optimization of reaction conditions for cyanide degradation using 5 mg ml-1 resting cells of microbial consortium. Plackett-burman design depicted that three variables viz. time, resting cells of strain RL2b and pH exhibit positive effect on cyanide degradation. The analysis of the quadratic regression model suggested that the model was very significant as correlation coefficient (0.847) closer to 1 denotes better correlation between the observed and predicted responses. The model was validated by performing the experiment under optimum conditions, which resulted in 63% cyanide degradation in 1 h reaction and complete degradation of 20 mM cyanide in 6 h. By performing factorial design, there was 1.3 fold (33%) increases in cyanide degradation.
Highlights
Cyanide containing wastewater is a potent health hazard for humans and components of ecosystems [1].The toxicity of cyanide is quite high due to its ability to poison the respiratory system by inhibiting the final transport of electrons from cytochrome C oxidase to oxygen, preventing production of ATP
RL2c, which were isolated from different habitats, were identified and cultivated together in consortium followed by optimization for in vitro cyanide degradation using response surface methodology
Three cyanide degrading bacteria were selected after screening of eighty six isolates
Summary
Cyanide containing wastewater is a potent health hazard for humans and components of ecosystems [1].The toxicity of cyanide is quite high due to its ability to poison the respiratory system by inhibiting the final transport of electrons from cytochrome C oxidase to oxygen, preventing production of ATP. The microorganisms reported to degrade cyanide include Bacillus sp. Azotobacter vinelendi degrades 69% of 4 mmol l-1 sodium cyanide while Bacillus sp. CN-22 has been reported to effectively degrade cyanide upto 200 mg l-1 concentration [7] and Serratia marcescens RL2b which is capable of degrading 780 mg l-1 of cyanide in a packed bed reactor completely [5]. Microorganisms have their own limitations in terms of growth in specific environment, substrate tolerance and degradation which is evident from previous reports. A consortium based approach followed in order to achieve higher substrate tolerance and degradation of cyanide. RL2c, which were isolated from different habitats, were identified and cultivated together in consortium followed by optimization for in vitro cyanide degradation using response surface methodology
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