83A-2 |
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D. CHUNG, Faculty of Marine Bioscience and Technology, Kangnung National University, Gangneung, 210-702, South Korea and S. M. Kim, Faculty of Marine Bioscience & Technology, Kangnung National University, 123 Jibyeondong, Gangneung, 210-702, South Korea. The use of an adequate amount of natural protease inhibitors is an effective way to extend the shelf life of many fermented seafoods such as surimi-based and salted fish products. This is because the inhibitors can retard the aging and other deteriorative processes caused by the action of endogenous and exogenous proteases, during the food processing and preservation. Natural protease inhibitors have been often obtained from legume, soy, animal blood plasma, milk, and egg white, however, little attention has been paid to the inhibitors from marine organisms, especially seaweeds. Considering high protein levels of red seaweed, we expect that the seaweed may contain effective protease inhibitors. Our objective was to isolate specific proteins that can inhibit proteases from a red seaweed, Porphyra yezoensis. Ethanol and water extractions were used to obtain protein extracts. The extracts were fractionated using the method of ammonium sulfate precipitation. The fractions of high protease inhibitory activities were dialyzed and further fractionated using an ion exchange chromatography. The size of proteins in the fractions of high inhibitory activities was determined using SDS-PAGE. The protease inhibitory activity was determined using a standard method based on the reaction of papain with azo-casein. Our results showed that the ethanol and water extracts of Porphyra yezoensis had notable protease inhibitory activities. The ion exchange chromatographic results showed that the protein fractions of longer retention time had higher inhibitory activities. For the ethanol extract, a 66 kDa protein was found to be primarily responsible for protease inhibition, while several proteins were isolated from the water extract. The red seaweed does contain protease inhibitors of different sizes. The isolated inhibitors may be positively charged as cystatins. The inhibitor from the ethanol extract is much larger than common 13kDa egg white cystatin.
Session 83A, Aquatic Food Products: Byproducts, mince and surimi
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