TOLERANCE AND LACCASE ENZYME SECRETION BY WHITE-ROT FUNGI IN CITRUS INDUSTRY WASTEWATER

BENITEZ SILVANA FLORENCIA; CHELALICHE ANIBAL SEBASTIÁN; ZAPATA PEDRO DARIO; SADAÑOSKI MARCELA ALEJANDRA; LEVIN, LAURA NOEMÍ; FONSECA MARÍA ISABEL

Congreso; SAIB-SAMIGE Joint Meeting 2020 ? Online; 2020

Asociación Argentina de Microbiología

Citrus-processing industries produce large volumes of wastewater (WW) characterized by a high content of organic matter, color, presence of pesticides, and terpenes. Due to their potential hazardous effect, several treatment systems have been proposed. Bioremediation using white-rot fungi (WRF) proved to be an eco-friendly effective strategy. Their ability to metabolize a variety of pollutants is attributed to the secretion of lignin-modifying enzymes, especially laccases (Lac). In this context, the screening of new isolates capable to tolerate and potentially bioremediate WW would contribute to the bioremediation research. The aim of this work was to assess the tolerance and Lac enzyme secretion of Irpex lacteus LBM 037, Phlebia brevispora LBM 036, Pleurotus pulmonarius LBM 105 and Trametes sanguinea LBM 023 in media supplemented with citrus WW. Tolerance in solid media was evaluated in 85 mm ø Petri dishes containing 12 mL of MEA (malt extract 12.7 g/L, agar 20 g/L) supplemented with WW (15, 30, 50 % v/v). One agar plug (5 mm ø) was inoculated; fungal radial growth was measured daily and analyzed using predictive mycology. τ (time to attain half the plate) was standardized as Δτ = τWWx ? τC, where τWWx were the values from supplemented media (x = concentration) and τC were the values from control without WW. A positive value of Δτ proved fungal growth inhibition. Assays in liquid media were performed in 250 mL Erlenmeyer flasks with 50 mL of ME (malt extract 12.7 g/L) supplemented with WW (15, 30, 50 % v/v). Flasks were inoculated with one agar plug and incubated for 10 d. Biomass production was assessed by mycelium dry weight and Lac activity in supernatants was determined. All assays were incubated under static conditions at 28 ± 1 °C. P. brevispora was able to tolerate all concentrations of WW in solid media (Δτ15=0.15; Δτ30=0.85; Δτ50=2.15). T. sanguinea and I. lacteus were capable of growing in 15 % v/v WW with the former being more tolerant (Δτ15=0.9; Δτ15=1.48, respectively). In liquid media P. brevispora was able to grow with up to 30 % v/v WW with no significant differences in average biomass production (3.61 ± 0.57 mg/mL). For T. sanguinea growth was observed with 15 % v/v WW with a significant increase in biomass production (4.20 ± 0.22 mg/mL). In the case of I. lacteus growth was possible with 15 % v/v WW with no significant differences in biomass (2.73 ± 0.20 mg/mL). As for Lac activity, P. brevispora presented the highest activity (155.25 ± 47.68 U/L) with 30 % v/v WW. T. sanguinea was able to secrete Lac (16.49 ± 6.69 U/L) in the presence of 15 % v/v WW similar to the control. Lac activity for I. lacteus was not detected in WW or controls. P. pulmonarius was not able to grow or secrete Lac in the presence of WW. This study allowed us to select P. brevispora LBM 036 as a promissory bioremediation agent for citrus WW treatment strategies.