在25～28．5℃条件下，于室外土池中培养小球藻18 d ，分别采集不同生长时期（延缓期、指数生长期、稳定期、衰亡期）的小球藻样本，采用毛细管气相色谱法测定脂肪酸的组成和含量，研究了土池小球藻在不同生长时期的总脂含量和脂肪酸组成的变化规律。试验结果表明，小球藻在指数生长期的粗脂肪含量（占鲜质量4．85％）明显高于其他生长期（占鲜质量1．44％～1．85％）。多不饱和脂肪酸和二十碳五烯酸的最高值出现在指数生长期，稳定期和延缓期次之，衰亡期最低。指数生长期、稳定期、延缓期和衰亡期的含量分别为总脂肪酸的23．37％、17．92％、17．53％和12．47％；二十碳五烯酸含量分别为总脂肪酸的17．92％、12．98％、13．02％和8．62％。因此，指数生长期末期或稳定期初期是室外土池培养小球藻的最佳收获期。%Alga Chlorella pyrenoidesa was cultured in the outdoor ponds at 25~28.5 ℃ for 18 days .The microalga were collected at different growth phases (delay phase ,exponential growth phase ,stationary phase and decay phase) .The effect of different growth phases on the total lipid content and the fatty acid composition of Chlorella pyrenoidesa were investigated .The fatty acids composition was determined by capillary gas-liquid chromatography .The results showed that the lipid content in the alga (4 .85% of fresh weight) gathering from exponential growth phase was significantly higher than those from the other three growth phases (1.44% ~1.85% of fresh weight ) .Maximum percentages of polyunsaturated fatty acid (PUFA ) and eicosapentaenoic acid (EPA ) were found in exponential growth phase ,followed by on stationary phase and delay phase ,and the minimum on decay phase .The percentage of PUFA and EPA were significantly decreased in stationary phase (17 .92% and 12 .98% ) , delay phase (17 .53% and 13 .02% ) ,and decay phase (12 .47% and 8 .62% ) relative to exponential phase (23 .37% and 17 .92% ) . Therefore ,late exponential growth phase or early stationary phase in the outdoor culture of Chlorella pyrenoidesa was the optimal harvesting phase .
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