The agri-food industry generates every year a considerable amount of waste residues (WR) that negatively impacts the environment and the economic well-being of people. For this reason, there is an urgent need to convert these by-products into value-added compounds. In parallel, efforts to reduce the use of synthetic pesticides have accelerated the development of natural biostimulants that enhance crop performance in an environmentally sustainable manner 1,2. Among emerging technologies, enzyme-assisted extraction represents a greener alternative to traditional non-enzymatic extraction, with benefits in terms of reduced solvent consumption and improved process scalability 3. In this study, different agro-industrial WR were subjected to enzymatic hydrolysis to obtain oligosaccharide-enriched mixtures that were tested for their bioactivity. Thermal alkaline pretreatment was applied to remove lignin, followed by enzymatic hydrolysis of the pretreated WR using commercially available endo-glycosyl hydrolases (e.g., endo-1,4-β-D-glucanase and endo-1,4-β-xylanase) and in-house produced xylanases. The obtained hydrolysates were analysed via HPAEC-PAD, showing the presence of both low molecular weight oligosaccharides of xylose (degree of polymerization 2-6) and unidentified peaks, likely related to higher molecular weight oligosaccharides. These mixtures contain cell wall-derived oligosaccharides that act as damage-associated molecular patterns (DAMPs), capable of eliciting plant immune responses 4. Oligosaccharide profiling revealed that xylanase-treated rice husk produced the most enriched hydrolysate, characterized by elicitor-active xylo-oligosaccharides. The different hydrolysates were applied to Arabidopsis thaliana to assess their ability to induce defence priming. Consistently, the xylanase-treated rice husk hydrolysate showed the highest efficacy, significantly enhancing resistance against the necrotrophic pathogens Botrytis cinerea and Pectobacterium carotovorum. Gene expression analyses confirmed strong activation of defence-related markers in treated plants, with no direct antimicrobial effect on the pathogens. Overall, these findings highlight the potential of DAMP-enriched biostimulants derived from enzymatically treated lignocellulosic waste as a sustainable strategy for crop protection.
[1]DOI:10.1016/j.emcon.2024.100410
[2]DOI:10.1016/j.plaphy.2024.108699
[3]DOI:10.1016/j.tibtech.2011.06.014
[4]DOI:10.1038/s41467-021-22456-x