Biotechnological potential of indigenous microalgal strains as sources of nutritional biomolecules, biostimulants, and biopesticidal agents

Authors: Aikaterini Gropali, Dimitra Matziri, Nikolaos Remmas, Shereen Basiouni, George Tsiamis, Asma Ben Salem, Salma Lasram, Mete Yilmaz, Mevlut Emekci,....

Ger. J. Microbiol. 2026. vol. 6, Iss. 2 pp:47-57
Doi: https://doi.org/10.51585/gjm.2026.2.0064

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Abstract:

Microalgae have recently been used as biostimulants, biofertilizers, and biocontrol agents, since their bioactive compounds can improve soil fertility and exhibit biopesticidal effects. In this work, microalgal strains were isolated from freshwater environments and examined against major phytopathogenic microorganisms, i.e., Verticillium dahliae, Phytophthora nicotianae, and Fusarium oxysporum f.sp. radicis-lycopersici. After isolating indigenous microalgal strains, their extracellular and intracellular protein and carbohydrate contents were quantified, their antimicrobial activity against the above phytopathogenic microorganisms was evaluated in vitro, and the potential phytotoxic effects of selected strains were assessed using seed germination tests. Among the microalgal isolates tested, no suppressive effect on the fungus V. dahliae and the oomycete P. nicotianae were observed. On the other hand, the application of the cultures of microalgal strains DMAZ3 and DMAVI resulted in approximately 25% inhibition of the growth of F. oxysporum f.sp. radicis-lycopersici. The addition of 10% and 25% v/v microalgal culture of strain DMAVI promoted the germination index of tomato seeds, whereas its application to cress seeds had no negative effects. In addition, microalgal culture DMAZ3 at a proportion up to 25% did not exhibit phytotoxic effect on both tomato and cress seeds, whereas this microalgal culture at 10% v/v resulted in a statistically significant increase of cress germination. Moreover, the majority of microalgal strains examined under autotrophic growth in BG-11 medium contained either high intracellular protein or extracellular carbohydrate content. In particular, microalgal strains DMA1, DMA3, and DMAVI growing in BG-11 had the highest intracellular protein content, ranging from 352.02 ± 16.12 to 389.71 ± 20.17 mg/g d.w, whereas the extracellular carbohydrate content of the microalgal strains DMAV, DMAII, and DMAVI growing in BG-11 medium was equal to 300.64 ± 13.52, 252.76 ± 35.94, and 139.79 ± 6.73 mg/g d.w, respectively. The above-reported results indicated the biotechnological potential of indigenous microalgae as sources of nutrients and as biopesticides and biostimulants.

Keywords:

Biopesticidal agents, Biostimulants, Microalgae, Fungicides, Phytoxicity, Photosynthetic microorganisms, Biopesticides

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