In the Pursuit of an Efficient Delignification From Pumpkin Seed Shells by the Polyextremophilic and Laccase-Producing Bacterial Isolate Halomonas Elongata Publisher



Adelpour T¹ ; Shahverdi AR¹ ; Amini M² ; Faramarzi MA¹ ; Mojtabavi S¹
Source: Biomass Conversion and Biorefinery Published:2025

Abstract

Biological delignification by laccase offers cost-effectiveness, energy efficiency, and environmental benefits. In this context, extremophiles and extremozymes enhance biomass pretreatment and lignin depolymerization, showing superior performance under harsh conditions. This study focused on isolating and characterizing a polyextremophilic bacterial isolate, identified Halomonas elongata, demonstrating laccase production under extreme circumstances. The enzyme production was enhanced to 719 U L−1 under the optimized conditions (pH 8.9, 1.5 M NaCl, 3.5 mM copper sulfate, and 1.58% w/v yeast extract). The extremozyme (183.4 U L−1), in combination with a 9.7 mM 1-hydroxybenzotriazole (HBT; as laccase mediator), effectively depolymerized lignin in pumpkin seed shells (30 mg mL−1) at 54.5 °C, obtaining a delignification efficiency of 95.1%. The enzymatic treatment significantly reduced lignin content (29.5 to 20.7%) while increasing cellulose accessibility (48.9 to 53.3%) in the biomass shells. Surface characterization using a scanning electron microscope (SEM) confirmed structural alterations in the biowaste, indicating successful lignin degradation. Gas chromatography-mass spectrometry (GC–MS) analysis of the byproducts revealed the formation of some valuable substances such as guaiacol, o-cresol, and ethyl 2-hydroxy-2-(4-hydroxyphenyl)acetate, providing insights into the bio-delignification pathway. This research demonstrates the promising potential of polyextremophilic laccases and enzymatic delignification for efficient and environmentally friendly depolymerization of lignocellulosic biomass. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.