Antimicrobial Activity of Stereum hirsutum Extracts Depending on the Nutrient Medium Composition

Background. The search for new antimicrobial compounds remains critically important due to growing antibiotic resistance. Basidiomycetes represent an important resource for selecting producers of metabolites with targeted activity, as their metabolic profile is highly dependent on cultivation conditions. Stereum hirsutum is known for its ability to synthesize antimicrobial substances; however, the dependence of its biosynthetic activity on cultivation conditions has been insufficiently studied.

The aim of the work. To study the effect of the nutrient medium composition on the biomass growth and antimicrobial activity of culture liquid and mycelial extracts of the basidiomycete S. hirsutum.

Material and methods. Submerged cultivation of the S. hirsutum 1 strain on six media with different carbon (glucose, molasses, glycerol) and nitrogen (yeast extract, peptone) sources. Preparation of ethyl acetate extracts from the culture liquid and ethanol extracts from the mycelium. Preparation of ethyl acetate extracts from the culture liquid and ethanol extracts from the mycelium. Antibacterial activity was assessed using the broth microdilution method against Gram-positive and Gram-negative bacteria to determine the minimum inhibitory concentration (MIC). Antifungal activity was evaluated by the agar diffusion method.

Results. Medium composition significantly affected biomass accumulation (ranging from 3.6 to 15.45 g/L) and extract yields (ranging from 40.5 to 184.5 mg/L). The highest antibacterial activity was observed in the extract obtained on the medium with glucose and yeast extract, showing an MIC of 320 µg/mL against Staphylococcus haemolyticus 585. The extracts demonstrated antifungal activity against Candida albicans, Candida auris, Aspergillus brasiliensis, as well as other clinically significant pathogenic fungi.

Conclusion. The qualitative composition of the nutrient medium allows for the targeted regulation of the antimicrobial activity of S. hirsutum extracts. To obtain extracts with high antibacterial and antifungal activity, it is advisable to use glucose and yeast extract as the carbon and nitrogen sources, respectively. Media with molasses provide the highest yield of submerged biomass. The obtained results provide the basis for the development of biotechnology for producing antimicrobial preparations based on S. hirsutum metabolites.

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