| Summary: | 碩士 === 國立中興大學 === 生物科技學研究所 === 103 === Abstract
Diatoms are the majority group of unicellular algae in nature. There are more than 100,000 species and approximately 200 genera so far discovered. Our laboratory collected diatoms and seawater from Kenting, the Port of Taichung and the Penghu islands. Almost all had their 18S ribosomal DNA (18S rDNA) sequence compared in BLAST and an optical microscope and Scanning Electron Microscopy (SEM) were also used to observe diatom shell patterns and frustule microstructure for further proof of identification. However, an additional four unclassified diatoms named AQ1, AQ11, AQ15 and PNP2 diatoms where then later classified. In this study, we determined that the Nitzschia genus is the closest in results to AQ1, but there was a newly identified sequence added to the BLAST data base, due to low similarity with existing Nitzschia diatoms, AQ11 was identified as Psammoneis pseudojaponica, AQ15 was identified as Navicula lanceolata, and PNP2 was identified as Navicula sp. They were then added to another 10 diatoms species to test the retention period of cold storage in 4oC. We then analyzed their total protein content to select the diatom species that could be applied in commercial aquaculture. In addition, we also tested f/2 medium adjustments and working volume amplification by using the above mentioned AQ1 and AQ11 and analyzed their total lipid content in order to test for possible future scale up conditions.
In order to culture them after different periods of time in the 4oC cold storage experiment, the diatoms were unfrozen and taken back the original temperatures. After one week of culturing following cold storage, they could all grow normally except for AQ15 and TPC5. For more than eight weeks of cold storage, the diatoms that could still be cultured were AQ1 (Nitzschia sp.), TPC14 (Odontella sinensis), and TPC11 (Skeletonema tropicum); for between 4-8 weeks, the diatoms that could be cultured were PNP2 (Navicula sp.)、TPC7 (Cyclotella meneghiniana), TPC8 (Chaetoceros sp.), and TPC10 (Thalassiosira minima); for less than four weeks, the diatoms that could be cultured were TPC13 (Chaetoceros sp.), AQ15 (Navicula lanceolata), TPC3 (Rhizosolenia setigera), AQ11 (Psammoneis pseudojaponica),TPC5 (Thalassiosira lundiana), and TPC6 (Thalassiosira tenera). According to their retention period in cold storage at 4oC, the total protein content for selected diatom species was analyzed to determine their viable application in commercial aquaculture. Under this subculture method revised, it was estimated that the shelf life of diatoms could be extended for at least one to two months under cold storage conditions (4oC) where the diatoms could be brought back to normal temperatures in order to re-culture them for a week; the f/2 medium adjustment and working volume amplification were also tested by using the above mentioned AQ1 and AQ11, and the results showed that the total lipid content of AQ1 increased 2X when the culture volume was amplified 5X and that the total lipid content of AQ11 was 9.5X more than in AQ1 when in the same culture medium and with the same volume.
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