Mycotransformation of anthracene by indigenous Trichoderma lixii and Talaromyces pinophilus isolates: insights into the metabolic pathways, enzyme profiles and acute toxicity

This study focused on the mycotransformation of a very prominent PAH, anthracene, and its acute toxicity reduction by Ascomycete fungi: Trichoderma lixii strain FLU1 (TlFLU1) and Talaromyces pinophilus strain FLU12 (TpFLU12), indigenously isolated from benzo[b] fluoranthene-enriched activated sludge. The results indicate that both the isolates TlFLU1 and TpFLU12 could tolerate anthracene exposure up to 1000 mg/L, with increased expression of ligninolytic enzymes: Laccase, Lignin peroxidase, and Manganese peroxidase. The mycotransformation of anthracene was observed to be growth-linked and mediated by the expression of the intracellular enzymes as the initial mechanism used by these strains followed by the ligninolytic enzymes with up to 56% and 38% anthracene degradation by TlFLU1 and TpFLU12, respectively, after 24 days with a concomitant change in pH from 5 to 4 (TlFLU1) and 6.2 (TpFLU12). The GC-MS and FTIR analysis of the samples indicate the appearance of metabolic intermediates: 9,10 anthracenedione and benzoic acid in TlFLU1 grown medium, while anthrone and 9,10 anthracenedione were detected in TpFLU12 grown medium. The mycotransformation of the compound followed a first-order kinetic model with an effective concentration (EC₅₀) of 262.3-266.1 mg/L, with a toxicity unit (TU) of 0.4% in Vibrio parahaemolyticus (6 h exposure) to each intermediate. Results show efficient mycotransformation of anthracene into a non-toxic state by TlFLU1 and TpFLU12.