Rhodococcus strain UCC 0010 as green biocatalyst for enhanced biodecolourization of Congo red through response surface methodology

The issue of unhealthy rivers in Malaysia has become a grave concern in the recent years due to the release of improperly treated industrial wastewater particularly from the textile plants. The present study capitalized on Rhodococcus strain UCC 0010 as a sustainable approach supporting eco-friendly and cost-effective measures to detoxify Congo red, a commonly found toxic diazo dye in textile finishing. Response surface methodology showed interaction effect between significant parameters was present where almost 100% decolourization at pH 2.8, 0.75% (v/v) carbon source and 35 °C was observed after 4 h of incubation. This strategy was able to reduce the incubation time by 83% and improved the decolourizing activity by 18% compared to conventional optimization method. This study revealed that the occurrence of Congo red decolourization was indeed mediated by Rhodococcus strain UCC 0010 and this strain used coconut waste as substrate for growth which was more economical than the commonly used yeast extract. The discovery of optimized decolourization at highly acidic condition and the occurrence of high titre of concentrated intracellular laccase activity (103.75 U/mg) suggested the presence of novel rhodococcal laccase which was able to decolourize 99% 0.2 g/L Congo red. Furthermore, phytotoxicity study observed that almost 100% germination of Vigna radiata and Vigna unguiculata occurred in treated Congo red solution indicating the ability of the strain to detoxify the dye. Collectively, these findings provided the platform to further improvise the function of the biocatalyst for viable application in treating textile wastewater.