Evaluation of mixed culture fungal strains for degradation of paraquat.

ABSTRACTThe potential of fungal mixed culture CI (Aspergillus niger + Phanerochaete chrysosporium), CII (Aspergillus niger AN400 + Trametes versicolor), and CIII (Phanerochaete chrysosporium + Trametes versicolor) was evaluated for paraquat removal, along with the individual potential of each fungus. In plate growth tests, only Trametes versicolor showed inhibition by paraquat (MI: 94.4%, 10 mg·L^-1) and the growth of Aspergillus niger and Phanerochaete chrysosporium was not inhibited by the pesticide, with maximum growth rates (K_max) of 2.136 day^-1 (R²: 0.821) and 1.632 day^-1 (R²: 0.713) at 40 mg·L^-1, respectively. Mixed culture CI outperformed CII and CIII, with K_max of 2.784 day^-1 (R²: 0.798; 50 mg·L^-1) and 2.352 day^-1 (R²: 0.939; 10 mg·L^-1), respectively, by Aspergillus niger and Phanerochaete chrysosporium. In an aqueous medium using a batch reactor, CI achieved the highest paraquat removal rate of 42.2% ± 2 at 50 mg·L^-1 without the addition of glucose, whereas non- mixed culture forms required glucose (5 g·L^-1) to achieve removals of 39.3% ± 3 for Aspergillus niger and 36.5% ± 0.7 for Phanerochaete chrysosporium. The synergy between these species was further confirmed by a paraquat removal rate (k) of 0.081 day^-1 (R²: 0.944) and a half-life (t_1/2) of 9 days. In contrast, with glucose in the medium, k and t_1/2 were 0.032 day^-1 (R²: 0.927) and 22 days. Thus, mixed culture CI demonstrated superior performance, making it suitable for efficient pollutant removal in bioreactors without the need for a cosubstrate.