Evaluation of mixed culture fungal strains for degradation of paraquat

<b>ABSTRACT</b>The potential of fungal mixed culture CI (<i>Aspergillus niger</i> + <i>Phanerochaete chrysosporium</i>), CII (<i>Aspergillus niger</i> AN400 <i>+</i> <i>Trametes versicolor</i>), and CIII (<i>Phanerochaete chrysosporium</i> + <i>Trametes versicolor</i>) was evaluated for paraquat removal, along with the individual potential of each fungus. In plate growth tests, only <i>Trametes versicolor</i> showed inhibition by paraquat (MI: 94.4%, 10 mg·L^-1) and the growth of <i>Aspergillus niger</i> and <i>Phanerochaete chrysosporium</i> was not inhibited by the pesticide, with maximum growth rates (<i>K</i>_max) of 2.136 day^-1 (<i>R</i>²: 0.821) and 1.632 day^-1 (<i>R</i>²: 0.713) at 40 mg·L^-1, respectively. Mixed culture CI outperformed CII and CIII, with <i>K</i>_max of 2.784 day^-1 (<i>R</i>²: 0.798; 50 mg·L^-1) and 2.352 day^-1 (<i>R</i>²: 0.939; 10 mg·L^-1), respectively, by <i>Aspergillus niger</i> and <i>Phanerochaete chrysosporium</i>. 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 <i>Aspergillus niger</i> and 36.5% ± 0.7 for <i>Phanerochaete chrysosporium</i>. The synergy between these species was further confirmed by a paraquat removal rate (<i>k</i>) of 0.081 day^-1 (<i>R</i>²: 0.944) and a half-life (t_1/2) of 9 days. In contrast, with glucose in the medium, <i>k</i> and t_1/2 were 0.032 day^-1 (<i>R</i>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.