Trichoderma harzianum AKH-5: A novel fungal isolate with antimicrobial efficacy for phytopathogen management and environmental remediation

Abstract

Trichoderma harzianum isolate AKH-5 is recognized as a biological control agent, effective in managing harmful phytopathogens while promoting plant growth and enhancing resistance to various stresses. In this study, a total of 140 morphological different fungal isolates were isolated and in primary screening isolate AKH-5 exhibited significant antifungal activity in vitro. Trichoderma harzianum isolate AKH-5 proved to be effective and was characterized morphologically, physiologically and through 18S rRNA gene sequencing and identified as Trichoderma harzianum. GC-MS profiling of the ethyl acetate extract identified 22 distinct bioactive compounds, including phenylethyl alcohol, dibutyl phthalate, and N-carbobenzyloxy-L-tyrosyl-L-valine, which possess antibacterial, antifungal and antioxidant properties. Further, in antibacterial assessment, AKH-5 extract exhibited significant antibacterial activity on microbial pathogens in a dose-dependent manner. The lowest MIC value against Escherichia coli was 8 μg/mL, indicating strong antibacterial activity. MBC values (32, 64 μg/mL) were higher than MIC values, indicating the need for higher concentrations for bactericidal effects and significant antioxidant activity with an IC₅₀ value of 90.78 μg/mL. The extract exhibited significant inhibition efficacy on Fusarium oxysporum, and Colletotrichum capsici, further moderate activity on Curvularia lunata, Alternaria alternata, and Rhizoctonia solani. The isolate AKH-5 showed good azo-dye degradation capacity and Triticum aestivum L. (wheat) seeds treated with dyes degraded with the isolate AKH-5 broth extract exhibited a germination rate of 98 %, compared to the untreated and control seeds which showed germination of 50 and 94 %, respectively. This study highlights the unexplored habitats as rich sources of diverse antifungal metabolite-producing fungi, which can be promising candidates for developing novel antifungal strains. Overall, the results demonstrate the beneficial role of AKH-5 in controlling phytopathogens and minimizing phytotoxicity through biodegradation of dyes for environmental remediation purposes.

Keywords: Antifungal activity; Antimicrobial activity; Antioxidant; Dye-degradation assay; GC-MS analysis; Secondary metabolites; Trichoderma harzianum.