Abstract:

Docosahexaenoic acid (DHA) is a very important polyunsaturated fatty acid, which plays a crucial role in many physiological processes in humans and animals. Because of fast growth rate and high DHA content, thraustochytrids show great potential in large-scale DHA production. In this paper, the DHA synthesis pathway, culture conditions affecting DHA production and the current status of pilot scale fermentation by thraustochytrids were introduced. Firstly, two DHA metabolic pathways of thraustochytrids including fatty acid synthase (FAS) pathway and polyketide synthase (PKS) pathway were summarized and described. Subsequently, three factors affecting DHA production by thraustochytrids, namely carbon and nitrogen sources, dissolved oxygen and temperature, were discussed. Then, the pilot scale up of DHA production by thraustochytrids was reviewed. Finally, the existing problems in the production of DHA by thraustochytrids were pointed out, indicating that future research emphasis should be given to screening high quality strains, investigating the key enzyme in the DHA biosynthesis and studying the pilot scale up technology. This article would be useful for the industrialized production of DHA by thraustochytrids.

Key words: thraustochytrids, docosahexaenoic acid, fermentation, metabolic pathway, influencing factors, pilot scale

摘要：

二十二碳六烯酸（DHA）是一种非常重要的多不饱和脂肪酸，能参与人及动物体内多个生理过程。破囊壶菌具有生长迅速、细胞内DHA含量高的特点，是工业化生产DHA的潜力菌。本文主要介绍破囊壶菌DHA代谢通路、影响破囊壶菌生产DHA的因素以及破囊壶菌中试发酵的研究现状。首先，对破囊壶菌合成DHA的两个代谢途径，即脂肪酸合成酶（fatty acid synthesis pathway，FAS）途径和聚酮合酶（polyketide synthesis pathway，PKS）途径进行总结和描述；其次，对影响破囊壶菌发酵生产DHA的三个主要因素（碳氮源、溶氧和温度）进行综述；随后，阐述了破囊壶菌发酵生产DHA的中试放大工艺的研究现状；最后，提出破囊壶菌发酵生产DHA过程中存在的问题，并指出进一步分离获得优质的破囊壶菌菌株、对其代谢途径和关键酶的研究以及中试放大工艺的研究是下一步研究的重点。通过对上述一系列问题进行综述，旨在为利用破囊壶菌工业化生产DHA提供一定的参考。

关键词: 破囊壶菌, 二十二碳六烯酸, 发酵, 代谢途径, 影响因素, 中试工艺