In-vitro antimicrobial activity and complement/macrophage stimulating effects of a hot-water extract from mycelium of the oyster mushroom Pleurotus sp.

•In vitro antimicrobial activity of aqueous extract from Pleurotus mycelia was found.•Activation of the alternative and presumably the classical pathways of complement•The extract enhanced the enzymatic activity of murine peritoneal macrophages.•A novel bifunctional approach to the nutraceutical potential of Pleurotus mycelium•Pleurotus mycelium is a renewable resource for developing new food bioingredients.

The study examined the in vitro antimicrobial and the complement/macrophage stimulating effects of a hot-water extract from mycelium of the oyster mushroom Pleurotus sp. The extract activated the microbial autolytic system of eight strains: seven autolyzing strains with intensity values (IS) ranging from 2.7% in Candida sp. to 36.1% in Saccharomyces cerevisiae, while autolysis was of 1.8% in one non-autolyzing strain (Bacillus cereus). The activation of the alternative pathway of the complement (APC) was dose and time dependent as judged by the lysis of rabbit red blood cells. Two main polysaccharide fractions of the extract significantly bind human immunoglobulin G (IgG) which could result in activation of the classical pathway of the complement (CPC). The extract (5–100 μg/well) enhanced the acid phosphatase activity in murine peritoneal macrophages to 133–184% compared to controls. The findings introduce a novel “bifunctional” approach (antimicrobial-immunomodulatory) to the nutraceutical potential of the Pleurotus hot-water mycelial extract.Industrial relevanceAt present, between 80% and 85% of all edible-medicinal mushroom products are derived from the fruiting bodies and only 15% are based on extracts from mycelia. The present study suggests that not only Pleurotus mushrooms but also their mycelia may be a good renewable and easily accessible resource for developing functional foods/nutraceuticals or even pharmaceutical agents with antimicrobial and immunomodulatory effects. Additionally, the application of the extract as food bioingredient could represent an innovative strategy for preventing and/or reducing the negative effects of food microbial spoilage. Hence the hot-water extract from mycelia of the oyster mushroom Pleurotus sp. is considerably relevant to the food and pharmaceutical industries.