Pleurotus albidus: A new source of milk-clotting proteases

Abstract

Researches have been done to discover new sources of microbial proteases with milk-clotting activity to replace the traditional rennet from calves. The aim of this study was to select a species of edible mushroom as milk-clotting enzymes producer using the submerged fermentation technology. From the six species evaluated, Pleurotus albidus was the one that expressed the highest value of coagulant ratio (21.60). The milk-clotting enzymes showed maximum activity at 60°C and pH 6.0. Iodoacetic acid presented the highest inhibition in proteolytic activity suggesting the presence of cysteine proteases in the crude extract from P. albidus. The enzymes did not present toxic action against human fibroblasts (MRC5) in the analyzed conditions and, for that reason, can be suitable to applications in food industry. This is the first report of milk-clotting enzymes production by the edible mushroom P. albidus

Milk-clotting proteases from Pleurotus albidus: an innovative alternative for the production of Minas frescal cheese

“…To assay optimum pH, proteolytic activity was determined at 40 ºC at different pH values using the following 0.1 M buffer solutions: sodium acetate (5.0 and 6.0), Tris-HCl (7.0 and 8.0) and Glycine-NaOH (9.0 and 10.0). For the pH stability, the crude extract was dispersed (1:1, v/v) in the following 0.1 M buffer solutions: sodium acetate (5.0 and 6.0), Tris-HCl (7.0 and 8.0) and Glycine-NaOH (9.0 and 10.0) and maintained at 25°C for 24 hours (Martim et al, 2017).…”

“…All samples were prepared in triplicate. Relative enzyme activities were determined according to the optimal conditions of pH and temperature (Martim et al, 2017).…”

“…Samples were incubated at 37 ºC for 60 minutes and residual enzyme activities were determined and compared to the control, which was incubated without the inhibitors and metal ions and corresponds to 100% of activity. All samples were prepared in triplicate (Martim et al, 2017).…”

“…These characteristics encourage the commercial cultivation of this species in many countries such as Argentina, Mexico and Brazil (Kirsch, Macedo, & Teixeira, 2016;Gambato et al, 2018). Studies have already shown that P. albidus synthesizes milk-clotting proteases in a liquid medium (Martim et al, 2017). However, the production of coagulant proteases by P. albidus grown in lignocellulosic residues and the application of these enzymes for the production of fresh cheeses has not yet been mentioned in the scientific literature.…”