Glucanase enzyme activity from rhizospheric Streptomyces spp. inhibit growth and damage the cell wall of Fusarium oxysporum

Abstract

Fusarium oxysporum, a phytopathogenic fungus responsible for fusarium wilt in more than 120 plant species, is primarily managed using synthetic fungicides, which pose environmental hazards. Therefore, alternative biological control methods are urgently needed. Actinobacteria isolated from maize rhizosphere, which produce β-1.3-glucanase enzymes that degrade fungal cell wall glucans, offer promising potential as biocontrol agents. This study aimed to evaluate glucanase activity, identify genes of actinobacteria, and assess their antifungal activity against F. oxysporum. Actinobacteria demonstrating glucanase production, Streptomyces sp. ARJ 22, Streptomyces tendae ARJ 42, Streptomyces sp. ARJ 44, and Streptomyces sp. ARJ 81, were selected. Streptomyces isolates exhibited activity values ranging from 10.38 to 24.08 U/mg of protein. The presence of the bglS gene, encoding endo-β-1.3-glucanase from glycoside hydrolase family 16, supports the production of glucanase. The amino acid sequence was constructed to 3D structural model. This model exhibited high similarity to endo-β-1.3-glucanase from Nocardiopsis sp. F96. In vitro assays demonstrated that all isolates inhibited hyphal growth of F. oxysporum. Direct inhibition assays showed an average inhibition of 26.18%, whereas the filtrate culture method showed 29.38% inhibition. Enzymes from Streptomyces sp. ARJ 44 was partially purified using acetone, resulting in a specific activity of 46.34 U/mg of protein and a purity increase of up to 1.92-fold. The purified enzyme inhibited the growth of F. oxysporum mycelia by 35.80%. This inhibition was confirmed by observing damage to F. oxysporum hyphae using scanning electron microscopy. The study concluded that the four Streptomyces sp. Strains producing β-1.3-glucanase enzymes have potential as biocontrol agents against F. oxysporum.