破囊壶菌Aurantiochytrium sp.细胞生长、油脂积累及二十二碳六烯酸(docosahexaenoic acid,DHA)合成与培养温度密切相关。该研究在摇瓶中考察了不同温度对破囊壶菌发酵的影响,结果表明,20~35 ℃的培养温度较利于破囊壶菌细胞的生长,而25~28 ℃的培养温度利于油脂的积累;虽然15 ℃培养时不利于菌体生物量积累,但能显著提高DHA占总脂肪酸的含量。基于以上实验结果,进一步在15 L发酵罐中采用了三阶段控温策略:发酵中前期(0~108 h)使用28和25 ℃的温度培养,以提高菌体生物量及油脂含量;发酵后期(108~120 h)以15 ℃低温培养促进DHA积累。采用此策略,发酵获得了116.80 g/L的细胞干重,总脂肪酸量达53.63 g/L,DHA产量为27.17 g/L,其中,油脂含量为45.92%,DHA占总油脂比例达50.66%。该研究为高密度发酵破囊壶菌生产DHA的大规模工业化提供了一种可行的方法。
The cell growth, lipid accumulation and docosahexaenoic acid (DHA) synthesis in Aurantiochytrium sp. is related to culture temperature. The effects of temperature variation on the fermentation of Aurantiochytrium sp. were studied in shake flask scale. The results demonstrated that the culture temperature of 20-35 ℃ had a positive effect on cell growth and the accumulations of total lipid were improved when cultured at 25-28 ℃.The ratio of DHA in total fatty acids increased significantly at 15 ℃ with depressed cell growth. Based on these results, a three-phase temperature shift strategy was developed. The cells grew at 28 ℃ and 25 ℃ aiming at increasing biomass and lipid content in the early middle stage (0-108 h), while DHA accumulation was enhanced at 15 ℃ during the anaphase (108-120 h) of the fermentation in 15 L bioreactor. The cell dry weight, total lipid content and DHA yield reached 116.80, 53.63 and 27.17 g/L, respectively. Lipid content of 45.92% and the ratio of DHA to total fatty acids up to 50.66% were obtained. This study provides an easy strategy for large-scale industrial production of DHA via high-cell-density fermentation of Aurantiochytrium sp.
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