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Comparison of differences in preparation of alginate oligosaccharides by different alginate lyases

學生姓名: 呂詠懷
指導教授: 方翠筠
學期: 113上
摘  要: AOS has gained considerable attention, and is widely applied in the agriculture, food, and medicine fields. For example, with a low M/G ratio and polymerization degree, AOS can induce cytokine synthesis, and significantly inhibit the pancreatic lipase, as well as the growth of prostate cancer cells. Therefore, seeking an efficient way to produce alginate oligosaccharides is of considerable significance. In the study, two different kinds of alginate lyase were investigated. First, AL07, was successfully screened and expressed in Pichia pastoris, and its characteristics were characterized. The secreted alginate lyase has a molecular weight of approximately 40.0 kDa and an activity of 45.4 U/mL. AL07 exhibits superior biological activity at pH 7.0 and 40 °C, with a preference for polyG substrates. Notably, the enzyme exhibits more than 60% relative activity over a pH range of 5.0 to 10.0. AL07 is also independent of ions and exhibits salt tolerance properties. Second, a novel alginate lyase, AlyRm3, was cloned from a marine strain, Rhodothermus marinus DSM 4252. The AlyRm3 showed optimal activity (37,315.08 U/mg) at 70 °C and pH 8.0, with the sodium alginate used as a substrate. Noticeably, AlyRm3 was stable at 65 °C and also exhibited 30% of maximal activity at 90 °C. These results indicated that AlyRm3 is a thermophilic alginate lyase that efficiently degrades alginate at high industrial temperatures (>60 °C).
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