Significance and Impact of the Study: Endolichenic fungi (ELF) are a unique group of organisms with the ability to sustain under challenging conditions and have rich and versatile metabolite profiles. The present study showed that several ELF, isolated from mangrove ecosystems could grow in low-density polyethylene (LDPE) amended media and showed signatures of LDPE biodeterioration. Qualitative and quantitative enzymatic assays of six extracellular fungal enzymes, having roles in polymer depolymerization were also performed. Results highlighted that six ELF species rich in enzymatic profiles were capable of LDPE biodeterioration.
Abstract
Fungal involvement in the biodeterioration of low-density polyethylene (LDPE) has received great attention in recent years. Among diverse groups of fungi, endolichenic fungi (ELF) are adapted to thrive in resource-limited conditions. The present study was designed to investigate the potential of mangrove-associated ELF, in the biodeterioration of LDPE and to quantify key-depolymerizing enzymes. A total of 31 ELF species, isolated from 22 lichens of mangrove ecosystems in Negombo lagoon, Sri Lanka were identified using DNA barcoding techniques. ELF were inoculated into a mineral salt medium, containing LDPE strips and incubated at 28 ± 2°C, for 21 days, under laboratory conditions. After incubation, biodeterioration was monitored based on percent reductions in weights and tensile properties, increments in the degree of water absorption, changes in peaks of infrared spectra and surface erosions using scanning electron microscopy. Out of 31 species, Chaetomium globosum, Daldinia eschscholtzii, Neofusicoccum occulatum, Phanerochaete chrysosporium, Schizophyllum commune and Xylaria feejeensis showed significant changes. Production of depolymerizing enzymes by these species was assayed qualitatively using plate-based methods and quantitatively by mass-level enzyme production. Among them, Phanerochaete chrysosporium showed the highest enzyme activities as (9·69 ± 0·04) × 10−3, (1·96 ± 0·01) × 10−3, (5·73 ± 0·03) × 10−3, (0·88 ± 0·01), (0·64 ± 0·06), (1·43 ± 0·01) U ml−1 for laccase, lignin peroxidase, manganese peroxidase, amylase, lipase and esterase, respectively.