| Summary: | 碩士 === 國立中山大學 === 海洋生物研究所 === 96 === The photoprotect compound mycosporine-like amino acids ( MAAs ) are a family of secondary metabolites can protect organisms exposed to solar ultraviolet radiation ( UVR ), only produced in the algae. Analyzed by HPLC, only Alexandrium minutum Halim ( Dinophyceae ) produces MAAs among seven marine microalgae species. The strains named AM-2、AM-3、AM-4 and AM-6 showed the positive results for producing the MAAs, but not AM-5. Researches on the stability the MAAs extracts from algal powder ( AM-3 ) hold at 4℃, 25℃ and 50℃ for 35 days and light expose. The results showed the MAAs gradually decayed after 35 days at 50℃, after exposed to UVR but decreased 48 % in one day and disappeared in two days. The growth and the MAAs produced in A. minutum ( AM-4, AM-6 ) under different salinity, nitrate concentration and UVR were analyzed to find their relationships. When the salinity increased ( 15 psu、25 psu、35 psu、45 psu ), the cell densities of both strain decreased significantly, but with similar MAAs composition and contents. In higher nitrate nutrient ( 2 N ), the cells produced more MAAs than those cultivated in lower nitrate ( N / 10、N / 2 ). Under the UV treatment with the deficient nitrate nutrient, the concentration of MAAs in A. minutum decreased after exposed to UVR for 14 hours. However, provided enough nitrate nutrient ( 2 N ), UVR can induced A. minutum to produce higher concentration of MAAs. These results showed MAAs may serve as a nitrogenous compound for intracellular storage, and not as a substance for osmotic adjustment. UVR is an important factor which induce MAAs produced in A. minutum.
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