Abstract

Environmental concern over the discharge of improperly treated textile wastewater has been on the rise. The present study explored the use of the limitedly studied, tropical Rhodococcus pyridinivorans for the decolourization of crystal violet, a typically encountered dye in the textile industry. The effect of agitation speed, temperature, pH, nutritional source, initial dye concentration and size of inoculum on crystal violet removal was evaluated using one-factor-at-a-time (OFAT) method. Decolourization of 0.6 mM crystal violet carried out at agitated mode showed 73 ± 3 % crystal violet removal efficiency in comparison to static mode (43 ± 2 %) after 24 h. This crystal violet removal efficiency escalated to 91 ± 2 % after optimizing the culture conditions at 45°C and pH 7 using maltose as carbon source and 12 % (v/v) size of inoculum. Furthermore, the optimization process reduced the incubation time to achieve almost complete decolourization by 67 %. Ultraviolet-visible (UV-Vis) analysis revealed that the decolourization of crystal violet primarily occurred through biodegradation. The findings from this study validated the potential of Rhodococcus pyridinivorans as an effective biocatalyst to remediate crystal violet. Rhodococcus pyridinivorans will be attempted to decolourize different triphenylmethane dyes namely malachite green in future studies.

Key words: Crystal violet; decolourization; optimization; one-factor-at-a-time (OFAT); Rhodococcus