Biochar enhanced the performance of microalgae/bacteria consortium for insecticides removal from synthetic wastewater

The presence of pesticides in aquatic environments has threatened marine food resources, aquaculture, fisheries and human health; therefore, two most used insecticides were removed during this study. Two photobioreactors, including biochar and Chlorella vulgaris/activated sludge (reactor 1), and Chlorella vulgaris/activated sludge (reactor 2) were run to remove chlorpyrifos (CPF) and cypermethrin (CYP). Proteobacteria, Bacteroidetes and Chloroflexi were the dominant phyla of activated sludge. The optimization performance of both reactors was conducted by response surface methods. The performance of first photobioreactor was better than that in the second reactor, achieving abatement of 88.80% CPF and 93.12% CYP, at 69.7 h contact time and 0.32 mg/L initial concentration. The toxicity of CPF and CYP to Chlorella vulgaris was monitored under 0–4 mg/L of insecticide concentrations and 0–72 h contact time. The minimum chlorophyll content (2 mg/L) and protein (16.7%), and maximum growth inhibition (89.7%) were recorded at 4 mg/L insecticides concentration and 72 h contact time. Moreover, molecular docking simulation for catalytic enzyme degradation of Proteobacteria, Bacteroidetes and microalgae was carried out using individual hydrolase enzymes: carboxypeptidase in microalgae, isochorismatase hydrolase in Proteobacteria and alpha-L-arabinofuranosidase in Bacteroidetes. Ligand-binding energy, affinity and dimensions of ligands-binding sites in the enzyme cavity were calculated in each case. Hydrolase is an enzyme group that offers a promising practical application for the degradation of CYP and CPF due to its cavity features. This analysis demonstrated the mode of interaction of ligands with hydrolase enzymes in different species.