The degradation of bisphenol A by laccase: Effect of biosurfactant addition on the reaction kinetics under various conditions

In this study, the enzymatic remediation of bisphenol A (BPA) from synthetic wastewater samples by laccase has been investigated in the presence (and also in the absence) of rhamnolipid (RL) biosurfactant. Different BPA, laccase and RL concentrations (spanning from 0.5 ppm to 2 CMC) have been utilized. Additionally, the kinetics and the extent of BPA removal at different temperatures, pH values and salinity levels have been examined in the presence and the absence of RL. The obtained results showed that the optimum concentration of RL is 1 ppm. At this RL concentration, about 23% increase in the BPA removal extent (after 2 h of treatment) was achieved. Additionally, the rate of BPA removal has been also boosted in the presence of RL. It has been observed that the addition of the biosurfactant improved, yet to varied degrees, both the extent and the kinetics of BPA removal under all examined conditions. Furthermore, the addition of RL did not alter the optimal reaction temperature (50 °C) and pH (5.8) of the BPA-laccase system. RL addition was still beneficial even under a high salinity level (29.22 g/L NaCl). The findings reported in this study suggest the potential application of RL as an eco-friendly and effective additive to enhance the rate and the extent of enzymatic treatment of phenolic wastewaters.