| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 89 === In order to investigate the optimum conditions for the recovery of native proteins from freeze-denatured fish muscle using NADPH-sulfite reductase, Escherichia coli CCRC 11634 was cultivated in a medium composed of 4.0 % sucrose, 0.4 % yeast extract and 0.4 % tryptone at pH 7.5 with shaking (100 rpm) at 37 ºC for 18 h, then harvested and sonicated. The crude enzyme was subjected to ammonium sulfate fractionation. Precipitate at 30 ~ 60 % saturation of ammonium sulfate was collected. The NADPH-sulfite reductase was purified to electrophoretic homogeneity by DEAE Sephacel and Sephacryl S-300 HR chromatographs. The recovery of total NADPH-sulfite reductase activity was 31.7 %, while the molecular weights was 119,000 estimated by Sephacryl S-300 HR gel filtration. The optimal pH and temperature for the enzyme activity were 7.7 and 25 ºC, respectively. It was inhibited by IAA, PMSF, NEM, PCMB, KCN, Hg2+, Fe2+, Fe3+, Ca2+, Co2+, Cu2+, Cd2+, Zn2+, Mn2+ and Ba2+. The reactive SH increased from 4.20 x 10-5 to 7.65 x 10-5 mol / g mince, while the gel strength increased from 109.4 to 211.2 g x cm when 0.03 unit / g surimi was added. SDS-PAGE suggested the high recovery of native actomyosin after the reaction with NADPH-sulfite reductase.
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