Assessment of the antifungal activity of actinobacteria isolated from soil impacted by solid waste

In the face of increasing microbial resistance, research on actinobacteria has gained prominence due to their ability to produce metabolites active against various microorganisms. This work evaluated the antifungal activity of metabolites produced by actinobacteria isolated from impacted soil. Isolation, identification, and extract production were performed, followed by antimicrobial tests using Agar Diffusion (10,000 μg/mL) and Minimum Inhibitory Concentration (1,000 μg/mL) against strains of Candida albicans (ATCC and clinical), C. parapsilosis (ATCC), C. krusei (ATCC), and C. glabrata (clinical). Toxicity tests with Tenebrio molitor and assays on biofilm formation and pre-formed biofilm were also conducted. Inhibition halos were observed for all microorganisms in the Diffusion test; only C. albicans ATCC90028 did not show activity at the MIC. Toxicological assays revealed low toxicity to Tenebrio molitor larvae. In biofilm assays, the highest concentrations reduced formation and pre-formed biofilm in all samples. At concentrations of 1/2 MIC and 1/4 MIC, there was an effect only on C. albicans ICO37 and C. glabrata ICV124. GC-MS analysis identified different compounds, including Hexadecanoic Acid (Palmitic and Isopropyl palmitate), Octadecanoic Acid (Stearic), Sesquiterpenes (Hedycaryol), and Prenylated Indole (4-(3-methyl-2-butenyl)-1H-indole), recognized for their antimicrobial and antibiofilm activities. The results indicate potential for the development of new antifungal bioactives, subject to further safety testing.