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Title: 不同分子量幾丁聚醣之抗菌及抗氧化活性
Antibacterial and antioxidant activities of chitosan with various molecular weights
Authors: Shun-Hsien Chang
張順憲
Contributors: NTOU:Department of Food Science
國立臺灣海洋大學:食品科學系
Keywords: 幾丁聚醣;抗菌;抗氧化
chitosan;antibacterial;antioxidant
Date: 2009
Issue Date: 2011-06-30T08:13:53Z
Abstract: 本研究以纖維素酶於 55oC水解 95%去乙醯度 (Degree of deacetylation) 幾丁聚醣 (DD 95),將不同水解時間水解液經離心及甲醇區分沈澱法得到不同低分子量幾丁聚醣 (low molecular weight chitosan, LMWC) 及幾丁寡醣,分析各幾丁聚醣之分子量及寡醣組成,並探討其抗菌活性及抗氧化活性。DD 95 於水解作用 0、1、3、6、9、18、24 小時所得水解液分離而得幾丁聚醣平均分子量分別為 300、156、72、29.2、7.1、3.3、2.2 kDa;於各水解時間之上清液均含有1~5醣。以G (+) 之Staphylococcus aureus BCRC 10780、Listeria monocytogenes BCRC 14845 及G (-) 之Escherichia coli BCRC 10675、Pseudomonas aeruginosa BCRC 10944 為測試菌株,培養液在pH 6.0時,DD 95及各幾丁聚醣抗菌活性皆隨分子量增加而增強,並以 300 kDa幾丁聚醣活性最強。 300、156、29.2 及 2.2 kDa幾丁聚醣對S.aureus及E. coli 最低致死濃度值 (minimal lethal concentration, MLC) 分別為 50、100、200、500 ppm 及 100、100、200、500 ppm。4 株測試菌株中以P. aeruginosa對幾丁聚醣抗性最強,各幾丁聚醣樣品對其MLC除了 2.2 kDa之外,其他均為 500 ppm。在pH 7.0 時,分子量大於 30 kDa之幾丁聚醣抗菌活性因溶解度降低而下降;而低於 30 kDa之 29.2、7.1、3.3、2.2 kDa幾丁聚醣仍具抗菌活性。幾丁聚醣之抗氧化活性均隨分子量減少而增加並呈濃度依存性,各抗氧化活性以 2.2 kDa幾丁聚醣最強,5000 ppm之 2.2 kDa幾丁聚醣對超氧陰離子清除率為 86.73 ± 0.26%,相當於 176 ± 2.67 ppm Quercetin,2000 ppm 之 2.2 kDa幾丁聚醣對DPPH自由基清除率為 63.40 ± 0.46%,相當於 113.64 ± 0.66 ppm Vit. C。相較於其他抗氧化活性,幾丁聚醣螯合亞鐵離子及清除ABTS+能力較弱,5000 ppm之 2.2 kDa幾丁聚醣螯合亞鐵離子率為 47.33 ± 1.44%,相當於 76.13 ± 1.39 ppm EDTA,濃度5000 ppm之 2.2 kDa幾丁聚醣清除ABTS+能力為 25.28 ± 0.55%,相當於20.75 ± 0.68 mM Trolox。
Chitosan with deacetylation degree of 95% (DD 95) was degraded by cellulase at 55oC for various periods, and the low-molecular-weight chitosan (LMWC) in the hydrolysate at each period was separated. The antibacterial and anti-oxidant activities of DD95 and LMWC with various molecular weights were investingated. The molecular weights (MW) of DD95 and LMWC from 0, 1, 3, 6, 9, 18, 24 hours-samples were 300, 156, 72, 29.2, 7.1, 3.3, 2.2 kDa, respectively. The oligosaccharides content of each period contain monomer to pentamer. Activities of antibacterial activities of DD95 and LMWCs at pH 6.0 and 7.0 against with two Gram positive strains of Saphylococcus aureus BCRC 10780 and Listeria monocytogenes BCRC 14845, and 2 Gram negative strains of Escherichia coli BCRC 10675 and Pseudomonas aeruginosa BCRC 10944. At pH 6.0 the antibacterial activity of chitosan increased with increasing of molecular weight of chitosan, with DD95 being highest. The minimal lethal concentrations (MLC) of chitosan with MW of 300, 156, 29.2, 7.1, and 2.2 kDa against S.aureus were 50, 100, 200 and 500 ppm, respectively, against E. coli being 100, 100, 200 and 500 ppm, respectively. Among 4 tested stains, P. aeruginosa was most resistant to chitosan. Except 2.2 kDa LMWC, the MLC of the rested 6 chitosan samples against P. aeruginosa was 500 ppm. However, at pH 7.0 the antibacterial activities of chitosan samples with 300, 156 and 72 kDa were greatly decreased; while chitosan samples with MW less than 30 kDa (29.2, 7.1, 3.3 and 2.2 kDa) were less affected by this pH change. Accordingly, these 4 smaller MW chitosan samples have much higher antibacterial activity at pH 7.0. Activities of scavenging DPPH, superoxide anion, ABTS+, and the Fe2+-chelating effect for LMWC samples were significantly increased with the decreasing MW of LMWC, and dose-dependence was observed, with 2.2 kDa LMWC being highest. The superoxide anion scavenging activity for 2.2 kDa LMWC at 5000 ppm was 86.76 ± 0.26%, and equal to 176.92 ± 6.27 ppm Quercetin; while its DPPH scavenging activity at 2000 ppm was 63.40 ± 0.46%, and equal to 113.64 ± 0.66 ppm Vit. C. Compared to other anti-oxidant activities, both DD95 and LMWC have weaker activity of chelating Fe2+ ion and scavenging ABTS+. The Fe2+-chelating and ABTS+ scavenging activity for 2.2 kDa LMWC at 5000 ppm were 47.33 ± 1.44 and 25.28 ± 0.55%, and equal to 76.13 ± 1.39 ppm EDTA and 20.75 ± 0.68 mM Trolox.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M96320034
http://ntour.ntou.edu.tw/ir/handle/987654321/15496
Appears in Collections:[食品科學系] 博碩士論文

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