Comparative analysis of antifungal and hydrolytic enzyme activities in the cyanobacteria Fischerella sp. and Alborzia Kermanshahica

Cyanobacteria are photosynthetic microorganisms capable of producing a wide range of bioactive metabolites with antimicrobial, enzymatic, and plant growth-regulating properties. Their extracellular metabolites and hydrolytic enzymes can degrade the cell walls of pathogenic fungi, making them potential candidates for the biological control of phytopathogenic fungi. In this study, the antifungal effects and hydrolytic enzyme activity of the cell-free extracts (CFE) obtained from the filamentous and unicellular cyanobacteria Fischerella sp. and Alborzia kermanshahica were investigated to evaluate their potential in fungal inhibition and bioactive compound production. Cyanobacterial strains were cultured in BG-110 and Z8 media. The antifungal activity of the cell-free extracts (CFE) obtained from the cyanobacterial cultures was determined using the disk diffusion method against the pathogenic fungi (Alternaria alternata, Fusarium solani, Fusarium oxysporum, Macrophomina phaseolina, Verticillium dahliae, and Phytophthora capsici). The activities of chitinase, protease, Filter Paperase (FPase), carboxymethyl cellulase (CMCase), xylanase, cellobiase, and cellobiohydrolase enzymes were evaluated using spectrophotometric methods. Total protein content and indole-3-acetic acid (IAA) hormone production were measured. The results indicated that Fischerella sp. exhibited significantly stronger antifungal activity compared to Alborzia kermanshahica. The mean inhibition zone diameter in Fischerella sp. was significantly greater than that of Alborzia kermanshahica against all tested fungi. Conversely, Alborzia kermanshahica produced higher levels of total protein (1.45-fold) and IAA (1.63-fold). Analysis of hydrolytic enzyme activity revealed that Alborzia kermanshahica produced significantly higher levels of protease (1.93-fold), xylanase (1.72-fold), and chitinase (1.92-fold) compared to Fischerella sp., while the activities of FPase, CMCase, cellobiase, and cellobiohydrolase were 1.73, 2.5, 1.71, and 1.74-fold higher, respectively, in Fischerella sp. than in Alborzia kermanshahica (p < 0.05). This study demonstrated that Fischerella sp., due to its stronger antifungal activity, is a promising candidate for the direct suppression of phytopathogenic fungi, while Alborzia kermanshahica, through its higher production of hydrolytic enzymes and IAA, may contribute to plant growth promotion and indirect disease control. These findings highlight the potential application of cyanobacteria in the formulation of biocontrol agents and the development of sustainable agricultural approaches. Future studies should focus on elucidating the molecular mechanisms underlying these activities and assessing their efficacy under field conditions.