Extraction, Purification And Characteristic Analysis Of The Protein From Auricularia Auricular

Auricularia auricular was one offungus which was homology of medicine and food, and its protein content was 9.85%. Now, most of researches about Auricularia auricular were focus on the extraction, purification and characteristic analysis, but there were few studies about Auricularia auricular protein. Besides, there was no report about strong electric field technology for the extraction of Auricularia auricular protein, ion exchange chromatography for the purification of protein and some determinations of Auricularia auricular protein properties. Alkaline process, strong electric field technology and Ultrasonic auxiliary alkaline were applied to the extraction of protein from Auricularia auricular, and ion exchange chromatography was applied to the purification of protein in this paper. Then physical and chemical properties, functional properties of Auricularia auricular protein was studied, and some functional properties of Auricularia auricular protein were compared with Soybean isolate protein.The work of this paper provided some academic bases for food processing about Auricularia auricular protein.The research contents and results were as follows:1. Study of extraction processThe influences to protein content and extraction yield from those three different extraction methods were compared, and conditions of the extraction were optimized by response surface methodology. The results of experiment showed that the suitable technological conditions of alkaline process were ratio of solid to liquid 1:90, extraction temperature 70 ℃, extraction time 2.5 hours and the concentration of lye 0.07mol/L.The suitable technological conditions of strong electric field technology were electric field intensity 2.5KV, impulse frequency 1600HZ, extraction time 2.Oh and ratio of solid to liquid 1:70. The suitable technological conditions of Ultrasonic auxiliary alkali were:ratio of solid to liquid was 1:90, extraction temperature 50℃, phaco time 50 min, concentration of lye 0.07mol/L and ultrasound power 300W.The protein contents of the three methods were 4.34%、3.69%、 4.72% respectively, and the corresponding extraction yields of protein were 44.1%、37.5%、 47.9%. Obviously, Ultrasonic auxiliary alkalinewas superior to Alkaline process and strong electric field technology, and its extraction rate and extracting effects were better while it needed less time.The extraction conditions for Ultrasonic auxiliary alkalineafter optimization by response surface methodology were:ultrasound power 300W, ratio of solid to liquid 1:92g/mL, phaco time 53 min, concentration of lye 0.07mol/L and extraction temperature 50℃. For these conditions, the content of Auricularia auricular protein was 4.76% and the extraction yield was 48.3%.2. Study of purification process:By taking the loss ratio of protein as index,the optimal process of activated carbon fading was determined. The deposition effects of protein were compared between isoelectric precipitation method and ammonium sulfate precipitation method.The precooling acetone was appliedto the second decolorationand decontamination. Also, the condition of DEAE-(cellulose) 52 purification process was optimized.Results of the experiment showed:the optimum parameter conditions of activated carbon fading were:activated carbon content 4%, bleaching time 30min and bleaching temperature 45 ℃.Isoelectric precipitation method was superior to ammonium sulfate precipitation method.The deposition rate of protein was high by this method, and its operation was simple and useful. Besides, isoelectric precipitation methodwas suitable for the protein that concentration was low. The effect of decontamination would be better if the protein was washed byprecooling acetone repeatedly. After that, the color of Auricularia auricular protein was light yellow, and the purity of protein was 41.6%. The condition parameters of DEAE-(cellulose) 52 purification process after optimization were:buffer solution (20mM Tris-HC1) pH7.2, loading quantity of sample 20mL and eluent flow rate 40r/min.For these conditions, the purity of protein was 71.3% after purification.3. Study of physical and chemical properties:The physical and chemical properties of Auricularia auricular protein were analyzed by SDS-PAGE, UV, FTIR,DSC and Amino acid component.The results of SDS-PAGE showed that the relative molecular mass focused on the interval of 50-100KD、35-40KD and 20-30KD.The results of UV indicated that there were absorption peaks at wavelengths of 220nm and 274nm.The Fourier transform-infrared (FT-IR) spectrum indicated that the secondary structure of the prepared Auricularia auricular protein was completed three helical arrangements structures.The DSC atlas analysisshowed that there was a endothermic peak,and the denaturation temperatures was 129.26℃, corresponding to enthalpy values of 393.79J/g. The content of essential amino acid of Auricularia auricular protein conformed to the Adult Standard Recommendation of the FAO/WTO.4. Study of functional properties:Solubility, foaming capacity/stability, emulsion capacity/stability and water/oil-holding ability of Auricularia auricular protein were studied. The functional properties were compared with Soybean isolate protein, and differences between two proteins at different pH and temperature were also studied. Results of the experiment showed:the foaming capacity and oil-holding capacity of Auricularia auricular protein were lower than Soybean isolate protein obviously, but the foam stability was superior to Soybean isolate protein. Besides, water-holding ability,emulsion capacity/stability and other properties were considerable to Soybean isolate protein.