Sugarcane bagasse as source of bioactive lignin: influence of pretreatment on the antioxidant and antibacterial activities

Sugarcane industry generates several by-products of particular interest in the context of a circular economy, due to their potential as a source of value-added ingredients. Bagasse is one of the main by-products, consisting of a fibrous fraction obtained after juice extraction. Sugarcane bagasse is composed of cellulose, hemicellulose, and lignin, with lower amounts of extractives and ash (del Río et al., 2015). Lignin is one of the most abundant renewable resources on earth and recognized as a profitable source of high value compounds. The main functions attributed to lignin in the plant are elasticity and mechanical strength. It is a complex aromatic macromolecule formed by the dehydrogenative polymerization of three phenylpropanoid monomers coniferyl, synapyl, and p-coumaryl alcohols. The antimicrobial activity of lignin is related to plant sources and attributed to the phenolic components, particularly the side-chain structure and its functional groups (Chauhan, 2020). The antioxidant activity of lignin is mainly attributed to the scavenging action of their phenolic structures on oxygen-containing reactive free radicals. For the antioxidant activity of the lignin, free phenolic hydroxyl groups and ortho-methoxy substitution in aromatic rings are essential. The structural characteristics of lignin depend on several factors including the botanical origin, and environmental growth and extraction conditions. The main objective of this work was to study the potential of lignin from sugarcane bagasse as antimicrobial and antioxidant agent and assess the influence of two different pretreatments - deep eutectic solvents and organosolv – on the biological potential.