Study of antimicrobial properties of Hericium fungal extracts

The study aimed to investigate the antimicrobial and antimycotic properties of 14 strains of fungi of the genus Hericium sp. To obtain antibiotic substances, the plants were grown superficially or deeply in a liquid nutrient medium, after which alcohol and ethyl acetate extraction was performed from the dried mycelium and culture liquid; for quantitative evaluation of antibiotic activity, plant extracts were tested by the method of discs and wells on solid nutrient medium, two test cultures of micro-mycetes, three test Gram-negative bacteria and three test Gram-positive bacteria; the minimum inhibitory concentration was determined by the method of dilutions by optical density. None of the strains of Hericium sp. showed antimycotic properties of plants. The antimicrobial effect of the culture liquid was generally stronger than that of the mycelial extracts. In the surface cultivation experiment, strong growth inhibition of test cultures was observed on days 7 and 14 of Hericium sp. cultivation. The growth inhibition zones of Escherichia coli were 17.5 cm for H. erinaceus 977 and 19.0 cm for H. erinaceus 2536; sterile zones on the plate from Micrococcus luteus were determined by diameters of 21.2 cm for the culture fluid of H. erinaceus 2530, 19.2 cm for the mycelial extract of H. erinaceus 977, and 17.8 cm for the biomass homogenate (BH) of H. erinaceus 2536. Long-term deep cultivation for 60 days contributed to the accumulation of antibacterial compounds effective against Staphylococcus aureus: the diameter of the sterile zone at 60 days was 30 cm for extracts from the biomass of H. erinaceus 2530, H. cirrhatum 2393, H. coralloides 2332. The strongest antimicrobial effect was recorded in the culture fluid of H. coralloides 2332 on the 21st day of growth (32.1 cm). The minimum inhibitory concentrations against S. aureus were determined to be in the range of 50-1,900 μg/ml for H. erinaceus 2530, H. coralloides 2332, and H. cirrhatum 2393. In general, a higher antibiotic activity was recorded against gram-positive microorganisms (S. aureus), and insignificant against gram-negative microorganisms (Pseudomonas aeruginosa). The data obtained can be used in further laboratory experiments on the identification and quantification of new antibiotics synthesised by fungi of the genus Hericium sp.