Effects of 2,4-D and environmental conditions on growth of P. crustosum strains and herbicide removal from rural-wastewater

Herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is mainly present in industrial and agrochemical wastewaters that are discharged into the environment. One way of offsetting its toxic effects is fungi-based bioremediation. This study aimed to evaluate the growth of two native Penicillium crustosum strains (RCP4 and RCP13) in the presence of 2,4-D, as well as their ability to remove it from rural wastewater. First, the strains were incubated on solid synthetic wastewater media with 1 or 5 mmol L⁻¹ of 2,4-D, at different pH values (5, 7, and 9) and temperatures (15, 25, and 37 °C) to simulate different wastewater conditions. Fungal colony ratios were measured daily to assess growth. Then, natural and sterile rural wastewater were supplied with 2,4-D (1, 2.5, and 5 mmol L⁻¹), inoculated with fungal pellets of each strain, and incubated for 21 days. The removal of the herbicide and the presence of 2,4-DCP, the main intermediate metabolite of 2,4-D degradation, were evaluated by UV-HPLC and mass spectrometry. The best growth values were obtained with 1 mmol L⁻¹ of 2,4-D at 25 °C and pH 7, both for RCP4 and RCP13. In rural wastewater, 2,4-D removal percentages were between 20 and 50% for RCP4 and between 10 and 70% for RCP13, under optimal growth conditions and at the three 2,4-D concentrations used. These are the first findings on the ability of two natively isolated Penicillium strains  to remove 2,4-D from rural wastewater, and they suggest that RCP4 and RCP13 could be promising candidates to decontaminate wastewater containing this herbicide through bioaugmentation.