MYCOREMEDIATION OF CITRUS WASTEWATER BY WHITE-ROT FUNGI IMMOBILIZED IN Luffa cylindrica

BENITEZ, SILVANA FLORENCIA,; SAGUCHI EY; ACOSTA GA; ZAPATA PD; SADAÑOSKI MA; LEVIN LN; FONSECA MI

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Citrus-processing industries produce large volumes of wastewater (WW) characterized by a highcontent of organic matter, presence of pesticides, and terpenes. Although several strategies weredeveloped for their treatment, white-rot fungi (WRF) have emerged as a promising alternative owingto their high tolerance and ability to degrade xenobiotics. WW can inhibit fungal growth due to thepresence of toxic compounds and/or bacterial proliferation, therefore fungal immobilization on lowcost lignocellulosic materials is proposed as an effective approach to increase their stability. The aimof this work was to evaluate two WRF immobilized on lignocellulosic material for the mycoremediationof real citrus WW. The strains Phlebia brevispora BAFC 633 and Pleurotus pulmonarius LBM 105 wereimmobilized on Luffa cylindrica. Citrus WW and L. cylindrica were kindly provided by CooperativaCitrícola Agroindustrial de Misiones Ltda. (Leandro N. Alem, Misiones) and Espudela (Jardín América,Misiones), respectively. The L. cylindrica was washed with tap water, rinsed with distilled water, ovendried at 40 ± 2 °C, and cut into 1 cm3 pieces. All the experiments were carried out in triplicate in 250mL Erlenmeyer flasks containing 1 g of L. cylindrica. Initial moisture was adjusted to 75 % w/w withCzapek medium (sucrose 30 g/L; K2HPO4 1 g/L; KCl 0.5 g/L; MgSO4 7H2O 0.5 g/L; NaNO3 20 g/L).Autoclave-sterilized flasks were inoculated with three agar plugs (~7 mm ⌀) of each strain and wereincubated for different time periods (0, 3, 6, 9, and 12 days) at 28 ± 1 °C under static conditions. Afterincubation, 50 mL of filtered citrus WW was added to the cultures, and flasks were incubated for 10extra days (treatment), destructive samples were taken every 48 h. The control consisted in WWwithout immobilized fungi. Supernatants were obtained by centrifugation at 4600 xg for 10 min.Chemical oxygen demand (COD) and toxicity were determined following standard protocols (openreflux method and Lactuca sativa seed germination/root elongation test, respectively). COD variationwas estimated as:% 𝐶𝐶𝐶 =(𝐶 − 𝐶)𝐶∗ 100where A and B are COD before and after treatment respectively. A significant COD reduction wasobserved for both strains. P. brevispora BAFC 633 reached 83.01 ± 1.81 COD reduction after 10 daysof treatment without prior incubation. For P. pulmonarius LBM 105 a 92.82 ± 5.18 % COD reductionwas determined after 10 days of treatment without prior incubation, and 94.26 ± 5.18 % with 9 daysof incubation. However, toxicity test showed that the treatment with P. pulmonarius LBM 105 without prior incubation was the most efficient for toxicity reduction. Treatments with P. brevispora BAFC 633were not able to reduce toxicity probably due to the persistence and/or production of toxicmetabolites. Therefore, these results show that the treatment with P. pulmonarius LBM 105immobilized in L. cylindrica is a promising alternative strategy for the mycoremediation of real citrusWW.