Pink oyster mushroom Pleurotus flabellatus mycelium produced by an airlift bioreactor-the evidence of potent in vitro biological activities

Four types of mycelial extracts were derived from the airlift liquid fermentation (ALF) of Pleurotus flabellatus, namely exopolysaccharide (EX), endopolysaccharide (EN), hot water (WE), and hot alkali (AE) extracts. Such extracts were screened for their active components and biological potential. EN proved to be most effective in inhibition of lipid peroxidation (EC50 = 1.71 ± 0.02 mg/mL) and in Cupric ion reducing antioxidant capacity (CUPRAC) assay (EC50 = 2.91 ± 0.01 mg TE/g). AE exhibited most pronounced ability to chelate ferrous ions (EC50 = 4.96 ± 0.08 mg/mL) and to scavenge ABTS radicals (EC50 = 3.36 ± 0.03 mg TE/g). β-glucans and total phenols contributed most to the chelating ability and quenching of ABTS radicals. Inhibition of lipid peroxidation correlated best with total glucans, total proteins, and β-glucans. Total proteins contributed most to CUPRAC antioxidant capacity. Antifungal effect was determined against Candida albicans ATCC 10231 (MIC: 0.019-0.625 mg/mL; MFC: 0.039-2.5 mg/mL), and towards C. albicans clinical isolate (MIC and MFC: 10.0-20.0 mg/mL). Comparison of cytotoxicity against colorectal carcinoma HCT 116 cells (IC50: 1.8 ± 0.3-24.6 ± 4.2 mg/mL) and normal lung MRC-5 fibroblasts (IC50: 17.0 ± 4.2-42.1 ± 6.1 mg/mL) showed that EN, and especially AE possess selective anticancer activity (SI values 3.41 and 9.44, respectively). Slight genotoxicity was observed only for AE and EX, indicating the low risk concerning this feature. Notable antioxidative and anticandidal activities, selective cytotoxicity against colorectal carcinoma cells, and absence/low genotoxicity pointed out that ALF-cultivated P. flabellatus mycelium could be considered as a valuable source of bioactive substances.