Systematic screening strategy for fungal laccase activity of endophytes from Otoba gracilipes with bioremediation potential

Fungal laccases are promising for biotechnological applications, including bioremediation and dye biotransformation, due to their high redox potential and broad substrate specificity. However, current bioprospecting methods for identifying laccase-producing fungi can be challenging and time-consuming. For early detection, it was developed a three-step, multi-criteria weighting system that evaluates fungal strains based on: First, the biotransformation capacity of three dyes (i.e., Congo red, brilliant blue G-250, and malachite green), at three different pH values, and with a relative weighting supported for the redox potential of each colorant. The relative decolorization coefficient (RDC), used as th2e first classification criterion, expressed their potential performance. Second, under the same conditions, laccase activity was estimated by observing the different degrees of oxidation of a given substrate. The selection criterion was the relative oxidation coefficient (ROC). Finally, laccase activity was quantified in submerged fermentations using three inducers (i.e., loofah sponge, Tween 80, and veratyl alcohol). This multicriteria screening strategy evaluated sixteen isolated endophytic fungal strains from Otoba gracilipes. The system identified Beltraniopsis sp. ET-17 (at pH values of 5.00 and 5.50) as a promising strain for dye biotransformation, and Phlebia floridensis as the best laccase producer, achieving a high activity of 116 μmol min⁻¹ L⁻¹ with loofah sponge as an inducer. In-vitro testing confirmed the efficacy of P. floridensis, with 53.61 % decolorization of a dye mixture (brilliant blue-Congo red. ratio 1:1) after 15 days of incubation. Thus, with the proposed screening strategy it was possible to highlight two species of interest at an early bioprospecting stage on a Colombian native tree poorly explored.