Characterisation and elicitor properties of extracellular polymeric substances (EPS) obtained from cultures of Sarocladium strictum isolated from rye rhizosphere

The rhizosphere is a habitat for a variety of microorganisms that can potentially be used for crop protection. Endophytic fungi are of particular interest because of their intimate interactions with plant roots. Nevertheless, a persistent challenge remains in the adaptation of microbial cultures to dynamic soil conditions, thus emphasising the importance of identifying strains capable of producing metabolites with elicitor activity. Extracellular polymeric substances (EPS) have been identified as promising candidates in this regard, given their ability to stimulate plant immune responses. The present study focused on optimising the production of. Extracellular polymeric substances (EPS) produced by Sarocladium strictum Th32Ag3 and evaluating its biological activity. The cultivation of the organism in sucrose-peptone medium resulted in a yield of 1.17 g/L of exopolysaccharide (EPS), consisting of 56% sugar cores, which were primarily composed of glucose, galactose, and mannose. The application of EPS to wheat seeds resulted in a substantial enhancement of defense-related enzyme activity, including phenylalanine lyase, tyrosine lyase, β-glucanase, and chitinase, without exerting any influence on oxidative stress enzymes such as catalase and peroxidase. Furthermore, EPS treatment resulted in a 30% increase in plant fresh weight. The elicitor effect of EPS was comparable to or even superior to that of chitosan, thus highlighting its potential as a sustainable biostimulant for strengthening crop resistance.