Biodegradation of some complex cyanide compounds, including sodium hexacyanoferrate (II) trihydrate [Na4Fe(CN)6·3H2O], potassium hexacyanoferrate (II) decahydrate [K4Fe(CN)6·10H2O], and potassium cyano-argentate [KAg(CN)2] by free cells of Pseudomonas resinovorans strain, was investigated in aqueous suspension as a function of pH, cyanide concentration, and initial glucose concentration. The minimum inhibition concentration (MIC) for each cyanide compound was determined while bacterial growth, ammonia generation, and glucose utilization were monitored during the experiments. The results indicate that P. resinovorans is able to degrade both the potassium and sodium cyanide complexes by using these compounds as sources of nitrogen. However, KAg(CN)2 was observed to inhibit the growth of the bacteria. The MIC values were determined to be 25 mM (10.55 g/L) and 75 mM (36.3 g/L) for K4Fe(CN)6·3H2O and Na4Fe(CN)6·10H2O, respectively, for P. resinovorans, whereas the maximum ammonia generated during cyanide biodegradation was observed at pH 5, and as expected, bacteria growth increased with higher glucose concentrations. Using P. resinovorans bacteria for the removal of cyanide is an innovative idea, and this study demonstrated the promising results. The findings of this study would be useful in designing a unit operation inoculated with P. resinovorans in a full-scale wastewater treatment plant for the treatment of cyanide-contaminated industrial wastewater.

biodegradation, ferro cyanide, potassium cyano argenate