Co-metabolism of thiocyanate and free cyanide by Exiguobacterium acetylicum and Bacillus marisflavi under alkaline conditions.
The continuous discharge of cyanide-containing effluents to the environment has necessitated for the development of environmentally benign treatment processes that would result in complete detoxification of the cyanide-containing wastewaters, without producing additional environmental toxicants. Since biological detoxification of hazardous chemical compounds has been renowned for its robustness and environmental-friendliness, the ability of the Exiguobacterium acetylicum (GenBank accession number KT282229) and Bacillus marisflavi (GenBank accession number KR016603) to co-metabolise thiocyanate (SCN-) and free cyanide (CN-) under alkaline conditions was evaluated. E. acetylicum had an SCN-degradation efficiency of 99.9 % from an initial SCN-concentration of 150 mg SCN-/L, but the organism was unable to degrade CN-. Consequently, B. marisflavi had a CN-degradation efficiency of 99 % from an initial concentration of 200 mg CN-/L. Similarly, the organism was unable to degrade SCN-; hence, this resulted in the evaluation of co-metabolism of SCN-and CN-by the two microbial species. Optimisation of operational conditions was evaluated using response surface methodology (RSM). A numeric optimisation technique was used to evaluate the optimisation of the input variables i.e. pH, temperature, SCN-and CN-concentrations. The optimum conditions were found to be as follows: pH 9.0, temperature 34 °C, 140 mg SCN-/L and 205 mg CN-/L under which complete SCN-and CN-degradation would be achieved over a 168-h period. Using the optimised data, co-metabolism of SCN-and CN-by both E. acetylicum and B. marisflavi was evaluated, achieving a combined degradation efficiency of ≥99.9 %. The high degradative capacity of these organisms has resulted in their supplementation on an active continuous biological degradation system that is treating both SCN-and CN-.
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa. Lukhayo.Mekuto@gmail.com.
Lukhanyo
L
Mekuto
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa.
Oluwadara Oluwaseun
OO
Alegbeleye
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa.
Seteno Karabo Obed
SK
Ntwampe
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa.|Department of Microbiology, Agricultural Research Council, Private Bag X5026, Stellenbosch, 7599, South Africa.
Maxwell Mewa
MM
Ngongang
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa.
John Baptist
JB
Mudumbi
Bioresource Engineering Research Group, Department of Biotechnology, Cape Peninsula University of Technology, PO Box 652, Cape Town, 8000, South Africa.
Enoch A
EA
Akinpelu
B. marisflavi; Biodegradation; Co-metabolism; E. acetylicum; Free cyanide; Thiocyanate