Enhancing Plant Immune Training and Protection through Damage- and Microbe-Associated Molecular Patterns from Anaerobic Digestate

Olive oil production is a major global agricultural industry that generates significant waste, particularly olive pomace, which poses environmental and economic challenges. Anaerobic digestion has emerged as a promising solution for its valorization into biogas and reducing its environmental impact. However, the resulting digestate remains underutilized and its long-term environmental impact is uncertain. Traditional disposal methods are costly and inefficient, underscoring the need for more sustainable approaches. In this study, olive pomace digestate was biorefined and its components were upcycled into soil amendments and plant immunostimulants. Metagenomic analysis revealed a diverse microbial community in the liquid fraction, including Luteimonas, Pseudomonas, and Caldicoprobacter. We obtained a MIcrobial Protein Extract (MIPE) from this biomass, containing precursors of microbe- and damage-associated molecular patterns including Flagellin, Elongation Factor Tu, and the phytocytokine Golven. Treatment with MIPE triggered a rapid plant immune response, characterized by increased hydrogen peroxide production, phosphorylation of mitogen-activated protein kinases, and the upregulation of defense-related genes such as CYP81F2, FRK1, and WRKY53. MIPE-induced priming enhanced Arabidopsis and tomato resistance to Botrytis cinerea and Pseudomonas syringae. Our findings highlight digestate as a source of bioelicitors, offering a sustainable alternative to chemical pesticides while enhancing plant immunity, valorizing olive mill waste and promoting sustainable agriculture.