Improved tolerance capacity and expression of degradation genes drive efficient removal of sulfamethizole by Chlorella pyrenoidosa

Abstract

In this study, the tolerance capacities and expression of key degradation genes of a microalgal species, Chlorella pyrenoidosa prior exposure to sulfamethizole (SFT) were investigated. The results showed that acclimated microalgae had higher tolerance capacities comparing to the wild type since the half-maximum effective concentrations at 96 h increased from 31.27 mg L−1 to 51.27 mg L−1. Meanwhile, the removal of SFT was enhanced by 45.5% after acclimation, which was mainly induced by biodegradation. Bioaccumulated SFT was 17.65 and 24.61 µg g−1 in wild type and acclimated species. Gradually increased content of reactive oxygen species might act as the secondary massager to monitor the cellular metabolic pathways including synthesis of energy sources and energy metabolism. Key biodegradation genes were identified with upregulated log 2-fold change of > 6. These genes may help to biodegrade SFT in acclimation process. This study tried to unravel the underlying mechanism of acclimation process in microalgal degradation of persistent sulfonamide antibiotics, which might be useful in increasing the engineering feasibility in treatment of antibiotics’ wastewater.