一株從南台灣淡水池中篩選出的微細藻類因為能夠產生橘紅色素而被篩檢分離出來；從這株新藻種產生橘紅色素的能力、細胞壁表面觀察到的肋狀經紋，以及核醣體18S subunit的序列相似度等三種特徵，我們認為這株藻類是文獻中單細胞藻類Coelastrella屬的其中一員，因而命名為Coelastrella sp. F50，中文名為經紋球藻。當以葉綠素穩定性作為細胞受損的指標時，此藻株可耐受攝氏45度達8小時以上，而大部分的葉綠素均未分解；另外在模擬戶外栽培環境的溫度變化下培養，本株新藻種也可在最高到達攝氏45度的溫度變化下快速生長，其倍增時程約為40小時。上述耐熱實驗皆說明本株新藻種適合在熱帶地區利用光反應器進行戶外大規模藻類生產。此株微藻在高鹽逆境且缺乏養分的環境下能夠加速生產橘紅色素，而且在此環境下培養七天之後到達22%的含油量；但此時的油脂含量仍少於實驗室另外一株產油藻種：Desmodesmus sp. F2在相同培養時間所能到達35%的含油量，因此新藻株較適合用來生產較高單價的食用油或橘紅色素。而由本株新微藻生產的橘紅色素在高效液相層析儀(high performance liquid chromatography)與NMR spectroscopy (核磁共振光譜)中的訊號顯示這些色素有可能是類胡蘿蔔素，並在高鹽逆境及缺乏養分的環境下被藻類生產來扮演抗氧化物質的角色。

A new species of reddish-orange pigment-producing microalga was isolated from a shallow pond in tropical Taiwan. Morphological and molecular evidence including meridional ribs on the cell wall, pigment production, and 18S rDNA sequence analysis suggest that this microalga is a species in the genus Coelastrella. Salt stress accelerated biosynthesis of the reddish-orange pigments, and large quantity of oil accumulated as the cells stressed under nutrient deficiency. This microalga could
sustain 45 °C for more than 8 hours indicated by the stability of its chlorophylls, which is a necessary trait for large scale outdoor cultivation using photobioreactors in tropical areas. The reddish-orange pigments could be separated into many fractions by HPLC, and signals from carotenoids were detected in a few fractions using NMR, suggesting these pigments may function as antioxidants among other roles.

Acknowledgements i
Abstract (in Chinese) ii
Abstract iii
Contents iv
Introduction 1
Materials and methods 4
Results and discussion 13
References 21
Figure legends 23
Figures 25
Tables 30

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