Exploring the untapped potential of solar pretreatment for deconstruction of recalcitrant Kraft lignin in fungal biotransformation

Abstract

Kraft lignin (KL) released from pulp and paper industries could cause severe environmental contamination. Appropriate effluent treatment is needed to mitigate the pollution. A novel strategy for biodegradation of KL by integrating photolysis with microbial oxidation process is reported. Results unveiled degradability of solar-treated KL (SKL) using a potential microbial strain: Trametes hirsuta MTCC-1171. Initially, KL was photodegraded by solar treatment. To analyze the chemical and physical changes in KL after solar treatment, scanning electron microscopy, Fourier transform infrared spectroscopy, and gel permeation chromatography were employed. Photolytic pretreatment induced depolymerization of chains in KL along with the cleavage of aromatic rings which made it amiable to further microbial degradation. SKL was used as a substrate to produce laccase during microbial degradation. The maximum activity of laccase of 7.1 ± 0.02 U/mL was observed on the 4th day of incubation. Microbial degradation products of photo-treated and untreated KL were identified using GC–MS. Intensification in KL degradation has been noticed along with the conversion of value-added products such as vanillin, valeric acid, and various higher alcohols. The results contribute an evidence of notable modifications of KL into value-added products using an innovative approach, which is eco-friendly and energy-efficient as well.