Exploring the potential of laccase from Grammothele sp. (pp464104.1) for polystyrene biodegradation: A promising approach for plastic waste management

Abstract

Laccase (EC 1.10.3.2) is a multicopper oxidase enzyme found in plants, fungi, and bacteria. It oxidizes various phenolic substrates through one-electron oxidations, causing cross-linking. Laccase can degrade polymers like lignin, a complex natural polymer of phenylpropanoid units linked by ether and carbon-carbon bonds. It also degrades polystyrene, a synthetic polymer derived from petroleum, composed of repeating styrene monomers that have a linear hydrocarbon backbone with phenyl groups. This study focuses on the laccase enzyme derived from Grammothele sp., a fungus recognized for its significant ligninolytic activity, and evaluates its potential in environmental biotechnology. The fungal strain was isolated and identified through ITS region phylogenetic analysis, confirming it as Grammothele sp. The laccase produced by the fungus was purified using Sephadex G-100 column chromatography, yielding a molecular weight of approximately 63 kDa as determined by SDS-PAGE. The enzyme exhibited optimal activity at 27 °C and pH 6.0, with notable plastic degradation observed under these conditions. Inhibition studies indicated sensitivity to specific inhibitors and metal ions, particularly Cu²⁺, Fe²⁺, Mn²⁺, and Cd²⁺, which reduced laccase activity. Importantly, the purified laccase demonstrated significant degradation of polystyrene, as confirmed by FTIR and SEM analyses, which revealed substantial chemical transformations and physical erosion of polystyrene particles. These findings highlight the enzyme's potential for mitigating plastic pollution. However, challenges such as enzyme inhibition and sensitivity to metal ions must be addressed. In conclusion, laccase from Grammothele sp. shows considerable promise for biotechnological applications in lignin degradation and plastic biodegradation, with future research aimed at optimizing its use in various environmental contexts.