Study On Extraction, Properties And Enzymatic Hydrolysis Of The Fruit Body Protein Of Coprinus Comatus

The basidiomycete, Coprinus comatus, is a kind of edible fungus reputed for its delicious taste and high nutrition. It contains a variety of functional active compounds. The production cost is low, with short production cycle, strong stress resistance and high yield. So it has broad propect for development. But the research on it remains rather weak, especially its protein.In this paper, the extraction process of the fruit body protein of Coprinus comatus was optimized and its functional properties were studied. The best protease for enzymolysis of the fruit body protein of Coprinus comatus was determinded and the technical parameters were optimized. The main results were presented as follows:(1) The effects of leaching solution pH value, temperature, ratio of solid to liquid, time on the extraction of the fruit body protein of Coprinus comatus were investigated. The optimum conditions of alkaline extraction were determined by orthogonal test plan and the isoelectric point was explored. In addition, the molecular weight distribution, amino acid composition and functional properties of the protein were studied. The results showed that the optimum extraction conditions were:pH at 11.5, temperature at 50℃, solid:liquid ratio(w/v) at 1:15, time at 50min. The isoelectric point was pH 3.8. At these conditions, the protein extraction rate was 24.3%, purity 80.7%.(2) The molecular weight of the extracted protein mainly distributed in 50-90kDa, 20-35kDa and 13～17kDa areas and contained relatively complete amino acid composition. The ratio of essential amino acid to total amino acid is 40.57%, essential amino acid to nonessential amino acids at 0.68, which determinded it a good protein. The protein had good solubility, emulsibility and foaming properties at high alkaline condition.(3) Five proteases (Papain, Alcalase 2.4L, Neutrase 0.8 L, Protamex, Flavorzyme 1000L) were used to hydrolyze the fruit body protein of Coprinus comatus at their suitable conditions. Based on the comparision of degree of hydrolysis (DH), protein recovery (PR), sensory evaluation and antioxidant activities of hydrolysates, Alcalase 2.4L was the most suitable protease for the protein, for its highest DH and PR, better sensory quality and antioxidant activities. The effects of enzymolysis temperature, pH, time, ratio of enzyme activity to substrate ratio ([E]/[S]) and substrate concentration on DH were studied. Response surface methodology was used to optimise the hydrolysis parameters of the fruit body protein of Coprinus comatus by Alcalase 2.4L. The results showed that the optimum conditions were pH at 9.0, temperature at 54.8℃, [E]/[S] at 6271U/g, time at 240min, substrate concentration at 1%. At these conditions, the DH was 24.05%.