Response surface methodology as an optimization tool to achieve an effective decolourization of crystal violet by the Malaysian Rhodococcus pyridinivorans strain

The extensive use of crystal violet, a known toxic dye in the textile industry, is concerning. The voluminous effluent generated from this industry requires proper treatment before discharge into the environment. The present study, therefore, exploits a tropical Rhodococcus pyridinivorans strain as an affordable and green approach to decolourize crystal violet from synthetic effluent which has not been endeavoured elsewhere. The presence of interactive effects between temperature (45 degrees C), the concentration of maltose (1.25% (w/v)) and the size of inoculum (20% (v/v)) was significant and resulted in a reduced incubation period to achieve 99.40% decolourization of crystal violet by 75% compared to the traditional optimization method. The generated model was highly significant since the average relative error between the predicted and experimental values was recorded at 3%, further confirming the dependability of the correlation for decolourization determination. The removal of crystal violet by free and immobilized cells obeyed the first-order kinetics with immobilized cells recording a 1.85-fold higher decolourization rate and 81% reduced half-life. Additionally, the immobilized cells were fit to be recycled for three cycles and the decolourized solution was free from toxicity as evidenced by the growth of Vigna radiata and Triticum aestivum which was comparable to distilled water (control). Collectively, these findings provided the platform to convert waste to wealth by detoxifying dye wastewater which can potentially be recycled for irrigation purposes using biocatalyst as the cheaper and greener alternative.

Automated summary

This study investigates an affordable and green approach using a tropical Rhodococcus pyridinivorans strain to decolourize crystal violet from synthetic effluent. The results show that the presence of interactive effects between temperature, the concentration of maltose, and the size of inoculum significantly reduces the incubation period and improves the decolourization efficiency. Immobilized cells also show higher decolourization rates and can be recycled for multiple cycles without toxicity.