| Barley pest is a new protein source which had been introuduced from abroad in the last two years and their nutritional value is higher than yellow mealworm.At present, their have no intensive researches and reports about this kind of insect. This paper used defatted powder of barley pest as raw material, extracted water dissolved protein, acid dissolved protein, mellow dissolved protein and alkaline dissolved protein with phosphate buffer, acetic acid solution, n-propanol solution and sodium hydroxide solution. Comparision of antioxidant activity of these kinds of proteins has also been studied. Optimize craft of water dissolved protein was been invested. The water dissolved protein and acid dissolved protein were gradual separated with ammonium sulfate precipitation, Sephades G-100 gel filtration chromatography and DEAE-Sepharose FF ion exchange chromatography, and the antioxidant activity of each component was studied. The main results were as follows:(1) The Barley pest protein was divided into water dissolved protein, acid dissolved protein, mellow dissolved protein and alkaline dissolved protein according to their dissolving abilities. Their antioxidant activities were also investigated. The results showed that the contents of water dissolved protein, alkaline dissolved protein, acid dissolved protein and prolamin accounted for 30.24%, 19.45%, 9.52%, and 4.43%, respectively. All of these four kinds of protein from Barley pest had antioxidant activity, the higher the concentration of protein was, the stronger the total reducing power and the scavenging power on·OH and O2·was。Water dissolved protein had the strongest reducing activity and scavenging power to superoxide anion. Acid dissolved protein had the strongest scavenging power to hydroxyl.(2)By measuring the extraction rate, the conditions of extraction were determined and optimized. The effects of ratio of liquid to solid, time, pH value, temperature and concentration of sodium chloride on extraction rate were studied in single factor test. On this basis, three factors (pH value, ratio of liquid to solid and temperature) and three levels test by quadratic regression rotational combinational design were studied. Through the test, it was found that the optimum conditions were: time 3h, ratio of liquid to solid 8:1,pH 9.0,and temperature 45℃, concentration of sodium chloride 0.15mol/L.Under these conditions, extraction rate of water dissolved protein was 40.26%. (3) The water dissolved protein of barley pest was extracted by means of salt solution and was purified by ammonium sulfate precipitation with Sephadex G-100 gel filtration and DEAE-Sepharose FF chromatography. The antioxidant activity of each component was also investigated. Results indicated that with Sephadex G-100 gel filtration, three components- P1,P2,P3 were found, and P2 which molecular weight is about 19KD exhibited stronger scavenging capability.With the further purification of DEAE-Sepharose FF chromatography, three components P2M1,P2M2,P2M3 were obtained, the scavenging rates of hydroxyl free radicals and superoxide free radicals of P2M2 reaching 99.42% and 55.11%%, respectively.(4) Acid dissolved protein was separated and fractionated into four portions F1,F2,F3 and F4 by using a Sephadex G-100 gel filtration chromatography column. When these fractions were tested for antioxidative activity, fraction F3 which relative molecular mass was 11KD was found to possess a strong antioxidative activity.With the further purification of DEAE-Sepharose FF chromatography, their were two components F3M1 and F3M2, the scavenging rates of hydroxyl free radicals and superoxide free radicals of F3M1 reaching 90.64% and 47.93%, respectively. |
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