Evaluation of mixed culture fungal strains for degradation of paraquat.

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ABSTRACT The 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 ( R ²: 0.821) and 1.632 day -1 ( R ²: 0.713) at 40 mg·L -1, respectively. Mixed culture CI outperformed CII and CIII, with K max of 2.784 day -1 ( R ²: 0.798; 50 mg·L -1 ) and 2.352 day -1 ( R ²: 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 ( R ²: 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 ( R ²: 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.