Study on the over-expression of β-D-galactosidase gene from Bifidobacterium bifidum and the production of high purity galactooligosaccharides
碩士 === 國立中正大學 === 化學工程所 === 95 === beta-D-Galactosidase (EC 3.2.1.23) catalyzes not only the hydrolysis of lactose into glucose and galactose, but also transgalactosylation reactions to form galacto-oligosaccharides (GOSs). A high transgalactosylation beta-galactosidase gene was isolated from chromo...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2007
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| Online Access: | http://ndltd.ncl.edu.tw/handle/99087942149491319112 |
| Summary: | 碩士 === 國立中正大學 === 化學工程所 === 95 === beta-D-Galactosidase (EC 3.2.1.23) catalyzes not only the hydrolysis of lactose into glucose and galactose, but also transgalactosylation reactions to form galacto-oligosaccharides (GOSs). A high transgalactosylation beta-galactosidase gene was isolated from chromosomal DNA of Bifidobacterium bifidum and amplified by polymerase chain reaction (PCR) with designed primers. The recombinate plasmid was constructed by inserting PCR fragment into plasmid pET-32a. The the recombinate plasmid was then transformed into Escherichia coli BL21(DE3) and overexpressed soluble target fusion protein.
The overexpressed recombinant enzyme was characterized and used for the production of galacto-oligosaccharides. The best transgalactosylation activity was at 37℃ and it was still good at 50℃. The highest galacto-oligosaccharide purity could be achieved about 65% when the lactose initial concentration of lactose was 60%. The result was better than the enzyme from Bacillus sp.
Low-content galacto-oligosaccharide syrups was converted into high-content galactooligosaccharides by yeast Kluyveromyces marxianus fermentation. The digestable sugars such as glucose, galactose, lactose and some other nondigestable disaccharides were removed. The final galacto-oligosaccharide purity up to 95% was achieved.
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