论文总字数：20692字

摘 要

DHA 因具有维护人体健康、预防人类疾病的功效，被广泛应用于医药和食品行业。目前，传统鱼油来源的 DHA 油脂由于易受环境、季节等的影响，已无法满足市场需求，于是人们逐渐将研究的热点转向了利用微生物发酵制备 DHA 油脂，而裂殖壶菌（Schizochytrium sp.）作为一株海洋破囊壶菌，因其具有生产 DHA 油脂的巨大潜力而成为当前微生物发酵产 DHA的常用菌种之一。

关键词：DHA 裂殖壶菌 脂肪酸 酸耐受性 耐酸驯化Abstract

DHA is known as “brain gold” for its efficacy in protecting human health against human diseases such as arteriosclerosis, rheumatism, and psoriasis. It is also widely used in the pHarmaceutical and food industries. At present, traditional fish oil-derived DHA oils are unable to meet market demand due to their vulnerability to the environment and seasons. Therefore, people have gradually turned their research hotspots into the use of microbial fermentation to prepare DHA oil, while (Schizochytrium sp.) Schizochytrium A marine thraustochytrid has become one of the commonly used strains of microbial fermentation DHA due to its great potential for producing DHA oil.

Acid stress is an environmental stress prevalent in microbial fermentation. The low pH caused by weak organic acids affects cell wall structure, changes the conformation of plasma membrane proteins, and increases the permeability of cells to ions and other small molecule metabolites. The intracellular pH is lowered, ultimately affecting microbial growth and product synthesis. Therefore, increasing microbial acid tolerance is critical for cell growth and efficient product synthesis. In this paper, adaptive evolution technology was used to improve the acid tolerance of Schizochytrium. Through acclimation and screening, strains capable of acid-tolerant Schizochytrium. were obtained, thereby improving the efficiency of Schizochytrium production under extreme conditions.

Key words: DHA ；Schizochytrium sp. ; unsaturated fatty acid ; Acid tolerance; Acid domestication

目录

摘 要 I

第一章 绪论 1

1.1. DHA概述 1

1.1.1 DHA的结构及理化性质 1

1.1.2 DHA 的生理功能 1

1.2. DHA合成研究 3

1.2.1 裂殖壶菌的生理结构 3

1.2.2 裂殖壶菌工业生产研究 3

1.3. 壶菌生产DHA的不可替代性 4

1.4. 微生物耐酸机制 6

第二章 材料与方法 7

2.1. 菌种与培养基 7

2.1.1 菌种 7

2.1.2 培养基 7

2.2. 培养方式 8

2.2.1 菌种驯化 8

2.2.2 菌种保藏 8

2.2.3 发酵培养 9

2.2.4 发酵表观数据分析 9

2.2.5 油脂含量的测定 9

2.2.6 甲酯化 9

2.3. 实验试剂及仪器 10

2.3.1 实验试剂 10

2.3.2 实验器材 10

第三章 实验结果及讨论 12

3.1. 裂殖壶菌在不同酸性条件下生长状况分析 12

3.2. 培养基pH4.0下驯化传代结果 13

3.2.1 镜检图样(每五代) 13

3.2.2 驯化中各代数据 14

3.3. 发酵表观数据分析 16

3.3.1 糖耗 16

3.3.2 pH变化 18

3.3.3 生物量变化 20

3.3.4 菌体中油脂含量 22

3.3.5 油脂中DHA的含量 23

3.4. 总结 25

第四章 展望与讨论 26

参考文献 27

绪论

DHA概述

二十二碳六烯酸（DHA）是ω-3多不饱和脂肪酸（PUFA）的一员，其作为保健产品和临床治疗药品的需求日益增长。微生物产生的富含DHA的脂质具有资源丰富，加工成本低，油成分稳定，污染低，氧化稳定性高等优点。已经发现并证明了几种微生物可以产生DHA，包括Crypthecodinium cohnii，AmpHidinium carterae，Thraustochytrium kinnei和Schizochytrium sp.，等。其中，破囊壶菌属（Schizochytrium sp.）是破囊壶菌科（Thyustochytriaceae）中的一种非光合作用的单细胞真核生物，它的合成产物中DHA的含量最高。毒理学评估显示其在食品中的拟议用途的安全性。 Schizochytrium sp.现在被认为是替代海鱼的良好DHA资源^[1]。

DHA的结构及理化性质

DHA 的生理功能

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