| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系 === 94 === Nattokinase (NK), also named as subtilisin NAT, is an enzyme primarily isolated from a traditional fermented food ‘Natto’ in Japan. It was recognized that oral administration of NK or Natto results in a mild and frequent enhancement of the fibrinolytic activity in the plasma. Activity of NK will be decreased because of weakness to acid environment in stomach. Poly-γ-glutamic acid (γ-PGA) biosynthesized from D-glutamic acid and L-glutamic acid by amide linkages between α-amino and γ-carbonxylic acid groups is water soluble, bio-degradable, edible and non-toxic toward humans. It is a potential material for making microcapsules with NK to prevent enzyme digestion in stomach. In this study, microcapsules were prepared by both dropping method and encapsulation unit method. The results obtained were as follows.
1. The particle size of microcapsules made by dropping method were larger and more irregular than using encapsulation unit method. Excellent microcapsules formed under the conditions of 5% γ-PGA Na+ and 6 L/min air flow rate. The coverage reached 82~86%, electron microscopy showed that microcapsule membrane was well coated by the γ-PGA Na+ level.
2. Original NK was sensitive to heat and acid. Its activity was gradually inactivated when heated at above 60℃ or kept at below pH 5. NK-100 and NK-200 still maintained 35% and 60 % activity respectively, after treated at below pH 4. And NK-100 and NK-200 still maintained 60% and 70% activity after treated above 50℃ for 1 hr. Microencapsulation with PGA raised the stability of NK.
3. Less NK survived in semi-gastric juice test (pH 1.4, pH 2 and pH 3) and pepsin also influenced NK activity. Combination of the intestine-released soft gel technology could extend the release of microencapsulated nattokinase to prevent from pormpt inactivation.
4. In summary, sodium γ-polyglutamate was potential material for making microcapsules. It could be used as a safe and protective delivery vehicle for drug administering and food industry.
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