Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/50928
標題: Characterization of alpha-galactosidase from Lactobacillus reuteri L22 and its application in fermented soymilk
Lactobacillus reuteri L22之alpha-半乳糖苷酶特性研究及其在發酵豆奶之應用
作者: 呂惠茲
Lu, Hui-Tzu
關鍵字: Alpha-半乳糖苷酶;Alpha-galactosidase;棉子糖類寡醣;發酵豆奶;raffinose family oligosaccharides;fermented soymilk
出版社: 食品科學系
摘要: 
本研究利用4MU-Gal及以p-NPG為基質,測試66株乳酸菌之-半乳糖苷酶的活性,選定一株高活性菌株Lactobacillus reuteri L22進行後續實驗。由L. reuteri L22產生之-半乳糖苷酶為胞內酵素,其粗酵素液對p-NPG最適反應條件是pH 5.0至5.5,45至50°C之環境,且在pH 4.5至7.5之穩定性佳,顯示其對不同之pH有相當寬廣的忍受性,在低於最適溫度之環境下可維持高活性至少4小時。以含有-半乳糖苷鍵結之醣類為碳源培養時,有較高之-半乳糖苷酶活性,尤其是使用棉子糖之效果最好(0.622 U/ml),除了果糖之外,其餘之醣類皆可支持L. reuteri L22之生長。實驗結果也證明-半乳糖苷酶可以分解天然基質,包括蜜二糖、棉子糖及水蘇四糖,適合應用於製糖工業以排除影響結晶之因子。將接種菌量1.25x108 CFU/ml之豆奶於37°C下發酵12小時,可將豆奶中之棉子糖與水蘇四糖完全去除,而使用-半乳糖苷酶粗酵素液(2 U),更可於8小時內將豆奶中之棉子糖類寡醣完全分解。發酵豆奶之感官品評顯示,以牛奶添加20%之發酵豆奶與10%果糖之樣品,最受到品評員所喜愛,而完全未經調味之發酵豆奶,較不被品評員所接受。因此,由L. reuteri L22產生之-半乳糖苷酶確實具有分解棉子糖類寡醣之能力,且可應用於發酵豆奶,排除引起脹氣之棉子糖類寡醣,未來有潛力製成類似乳酸飲料或酸豆奶之成品。

Sixty six strains of lactic acid bacteria were screened for their -galactosidase activity with two kinds of substrates, 4MU-Gal and p-NPG, respectively. Among them, Lactobacillus reuteri L22 showed the highest activity and was chosen for further study. Alpha-Galactosidase from L. reuteri L22 was first demonstrated to be an intracellular enzyme. The optimal activity of the crude enzyme from L. reuteri L22 was characterized by using p-NPG as substrate at pH 5.0~5.5 and 45~50˚C. The crude enzyme retained good stability between pH 4.5 to 7.5 and showed high enzymatic activity at least 4 hr under the optimal temperature. When L. reuteri L22 was incubated with different -D-galactosyl oligosaccharides as carbon sources, the bacterial cells expressed higher -galactosidase activity, especially when raffinose was used (0.622 U/ml). All sugars could support the growth of L. reuteri L22, except for fructose. The results in this study also proved that -galactosidase from L. reuteri L22 could hydrolyze natural substrates, including melibiose, raffinose, and stachyose. The raffinose and stachyose in soymilk could be totally hydrolyzed when the soymilk was fermented 12 hours by L. reuteri L22 with the initial inoculation of 1.25x108 CFU/ml. When treated with 2 U of the crude enzyme from L. reuteri L22, after 8 hour of reaction, raffinose and stachyose in soymilk disappeared completely. The sensory evaluation of the fermented soymilk produced by L. reuteri L22 was conducted by a consumer sensory panel. Milk plus 20% fermented soymilk and fermented soymilk plus 10% fructose were the most favorite products and the unadorned fermented soymilk was not acceptable to the panelists. To summary, the -galactosidase of L. reuteri L22 was capable of degrading raffinose and stachyose and could be applied in soymilk fermentation for the removal of raffinose family oligosaccharides in soymilk to resolve the flatulence problem caused by them. It has the potential in the development of the lactic acid beverage-like or soyoghurt products.
URI: http://hdl.handle.net/11455/50928
Appears in Collections:食品暨應用生物科技學系

Show full item record
 

Google ScholarTM

Check


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.