Enzymatic activity of extracts from higher fungi for manufacturing fermented dairy products

Abstract

The present study investigates the enzymatic activity and chemical composition of extracts obtained from the substrate mycelium of higher fungi. The investigated object is the biomass of fungi Piptoporus betulinus (substrate mycelium) gathered after solid-phase cultivation on natural substrate. The extracts were obtained using distilled water (pH=7.0), acetate (pH=4.7) and phosphate (pH=7.4) buffers, and Mcllvaine buffer (pH=4.0). Milk-clotting, proteolytic, cellulosolytic and lipolytic activity, as well as protein content, were determined in both aqueous or buffer extracts. As a result, the values of cellulosolytic (3.75–3.90 units/g), lipolytic (40.00–44.24 units/g) and milk-clotting (65.80–66.60 units/mL) activity of the substrate mycelium was determined. These values differ slightly in the extracts prepared on distilled water and buffers. Moreover, the concentration of protein substances in the native aqueous extract from the substrate mycelium of P. betulinus was 14.50 mg/mL. The values of proteolytic activity varied from 0.22 to 0.78 units/mL. Distilled water was found to be the most effective solvent for achieving high values of milk-clotting activity. Extract purification by microfiltration or with bentonite leads to a significant decrease in protein concentration (up to 5.90 mg/mL), cellulose(up to 1.40 units/g), lipo(up to 5.30 units/g), and proteolytic (up to 0.11 units/mL) activity, and an increase in milk-clotting activity values (up to 285.80 units/mL). The bentonite sorbs cellulosolytic, lipolytic, and non-specific proteolytic enzymes, resulting in a noticeable increase in the value of milk-clotting activity. In the aqueous extract of P. betulinus fungi, a high ratio of milk-clotting to proteolytic activity was found with a value of 2598.20. This may lead to an increased yield and improvement of the organoleptic properties of cheese and its storage period.