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Presence of thiocyanate (SCN -) is a problem of considerable interest in many industrial wastewaters, where this contaminant often appears accompanied by secondary sources of carbon, nitrogen and/or sulphur. In order to understand the effect of these compounds on the biodegradability of SCN -, this work investigates how the bacterium Pararacoccus thiocyanatus utilises the three elements that form the molecule of thiocyanate and compare this behaviour with those obtained in presence of other sources of N, S and C. Result showed that the bacterium was capable of utilizing thiocyanate as the sole substrate, achieving specific biodegradation rates of approximate 1.20 mg SCN -(mg cell·h) -1 and eliminating initial thiocyanate concentrations up to 5,000 mg L -1 . Experimental data were successfully fitted to a Teisser model, assuming the existence of substrate inhibition obtaining values of μ max of 0.059 h -1 , K s of 790 mg L -1 and K i of 6,520 mg L -1 for free mineral medium. Presence of additional carbon and nitrogen sources implied catabolic repression of the biodegradation of thiocyanate. In this case, only concentrations lower than 3,500 mg L -1 could be treated, obtaining specific degradation rates of around 0.70 mg SCN -·(h·mg cell) -1 . Tessier model values showed a higher maximum specific growth rate (0.344 h -1 ), changing also the values for affinity and inhibition constants (1,150 mg L -1 and 1,730 mg L -1 , respectively).

Phenolic and cyanide compounds, which frequently appear mixed in several industrial effluents, are difficult to be biodegraded under certain conditions. In this work, salicylic acid (SA) and thiocyanate (SCN -) were selected as model pollutants of these two families and experiments of biodegradation with specific microorganisms were developed. It was found that the best wellknown bacteria able to biodegrade each one of these pollutants, Pseudomonas putida for SA and Paracoccus thiocyanatus for SCN -, do not biodegrade the other one. Therefore, the co-culture was required, producing interesting interaction phenomena. When both pollutants were simultaneously biodegraded, a commensalism effect was observed improving SCN -removal. Experimental data for SCN -and SA removals were successfully fitted to zero reaction kinetic orders, with induction time in the case of SCN -, and substrate dependences were fitted to Tessier models. A flow cytometry method was developed and employed to obtain the evolution of the viable, damaged and dead cells for different substrate concentration and the degree of agglomeration in the co-culture experiments.