Biochemical and extracellular mechanisms of plastic degradation by epiplastic microalgae: A novel approach on...

Plastics distinct characteristics make them significantly important for various applications in modern human activities. However, due to overexploitation and urban expansion, they pose a substantial threat to lentic freshwater ecosystems. The present study focused on epiplastic microalgae that can potentially degrade diverse domestic plastics by altering cellular metabolism. An adaptive response of epiplastic microalgae shows variations in primary and secondary metabolites, facilitating the production of Reactive Oxygen Species, causing oxidative damage to plastics. Biodegradation activity was assessed by tensile strength and weight loss of treated plastics up to 27 ± 2% on High Density Polyethylene (HDPE), and 21 ± 2% on Low Density Polyethylene (LDPE). The Fourier Transform Infrared Spectroscopic analysis of treated plastics with Stigeoclonium (PD1), Uronema (PD2) and Nostoc (PD7) has revealed peaks at CCH: CH stretch (Alkynes), CN (Aliphatic Amines),and CH wag -CH₂ (Alkyl Halides) on treated HDPE as well as HCO: CH stretch (Aldehydes) on treated LDPE plastics. Gas Chromatography-Mass Spectrometry studies confirmed the release of Fatty Acid Methyl Esters of Hexadecanoic acid, Eicosanoic acid, and Cyclopropane in the treated microalgae (PD2 & PD7). Structural degradation was confirmed using Scanning Electron Microscopy and Atomic Force Microscopy, which revealed an increase in surface roughness from 31.9 nm to 207 nm at 5 µm². Uronema trentonense (GenBank- PX724094) creates oxidative damage by the release of ROS due to overproduction of pigments and lipids, which subsequently activates the lipase-like enzyme that has significantly degraded the HDPE and LDPE plastics.