论文总字数：15634字

摘 要

二十二碳六烯酸（DHA）是一种ω-3型的长链多不饱和脂肪酸，具有促进大脑发育、降低血脂等作用，目前已广泛应用于食品、医药等行业。裂殖壶菌是应用到工业化发酵生产DHA最为广泛的菌株之一，它是一种海洋真菌，具有生长速度快、油脂产量大以及DHA含量高等优点。

本实验在35℃条件下对裂殖壶菌进行耐热驯化，通过高温驯化来增强其耐热性，旨在缩短发酵周期、提高DHA的产量并降低成本，在裂殖壶菌耐热驯化过程中，其生物量和糖耗逐代增多。对在35℃下生长优良的第20代驯化菌进行发酵性能检测，将该驯化菌与原始菌置于30℃和35℃条件下进行发酵，并对其生物量、糖耗、油脂产量及DHA含量进行检测分析。

在30℃下进行发酵，原始菌与驯化菌的生物量分别为48.7g/L和56g/L，DHA产量分别为7.16g/L和9.37g/L，相较于原始菌株，驯化菌株的DHA产量提高了30.87%。在35℃下进行发酵，原始菌与35℃驯化菌的生物量分别为25.9g/L和45.6g/L，DHA产量分别为2.53g/L和6.96g/L，驯化菌的DHA产量比原始菌的高175.10%。原始菌在35℃下的发酵能力远低于30℃下的，驯化菌的则相差不大。

关键词：裂殖壶菌 耐热驯化 发酵 代谢产物

Adaptive Evolution and Metabolic Mechanism of Schizochytrium sp under High Temperature Stress

Abstract

The docosahexaenoic acid(DHA) is a kind of long chain poly-unsaturated fatty acids that can promote brain growth and decrease bloodlipid, which make it used widely in food and medicine idustry.The most used microorganism to produce DHA is a kind of ocean fungi named Schizochytriumsp ,who has advantages of growing quickly as well as high DHA percentage in lipid.

Cultured in 35℃ continuously could inhance Schizochytriumsp’s tolerance to heat pressure gradually,as a result, the evoluted fungi would produce more DHA and have a lower cost.In the experiment we found the latter generation always produced more biomass and consumed more glucose than the former.Then we put 20th generation in fermentation and compared some indexes with the natural Schizochytrium sp,such as biomass,lipid content and DHA percentage.

While in fermentation at 30℃ and 35℃, the evoluted fungi both produced more biomass,lipid and poly-unsaturated fatty acids than the natural Schizochytriumsp.The yield of DHA produced by evoluted fungi was 9.37g/L in fermentation at 30℃ ,and 7.16g/L by natural Schizochytriumsp.Their biomass were 56g/L and 48.7g/L.The former produced 30.87%DHA yield more than latter. When fermentated at 35℃,the former produced 6.96g/L DHA and had a biomass with 45.6g/L,the latter produced 2.53g/L DHA and had a biomass with 25.9g/L.The yield of DHA increased 175.10% after evoluted.The fermentation level of the natural Schizochytrium sp at 35℃ was much lower than that at30℃,while the evoluted fungi only had a small dispariy between two fermentate conditions.

Key Words: Schizochytriumsp; Temperature stress; Fermentation; Metabolite

目 录

摘要 I

Abstract II

第一章 文献综述 1

1.1引言 1

1.2多不饱和脂肪酸及其生产途径 1

1.2.1多不饱和脂肪酸 1

1.2.2微生物法 2

1.3裂殖壶菌的耐热驯化 2

1.3.1菌种驯化 2

1.3.2耐热驯化 3

1.4多不饱和脂肪酸合成机制 3

1.5展望 4

第二章 裂殖壶菌的耐热驯化及代谢机制 5

2.1引言 5

2.2材料与方法 6

2.2.1菌种 6

2.2.2实验仪器 6

2.2.3实验试剂 6

2.2.4培养基 8

2.2.5裂殖壶菌的耐热驯化 8

2.2.6发酵培养及部分代谢产物的测量 9

2.3结果与分析 10

2.3.1耐热驯化生长情况 10

2.3.2原始菌与驯化菌在30℃下发酵对比 11

2.3.3原始菌与驯化菌在35℃下发酵对比 12

2.3.4两组发酵的对比 13

第三章 讨论 13

参考文献 15

致谢 17

第一章 文献综述

1.1引言

随着生活水平的不断提高，人们越来越多地追求饮食更加健康、富含营养，对功能性油脂的需求量也随之增加。其中，以二十碳五烯酸、二十二碳六烯酸为代表的长链多不饱和脂肪酸具有促进大脑发育、预防心脑血管疾病等作用，目前已广泛应用于食品、医药等行业^[1]。

传统上以动植物油脂为原料生产多不饱和脂肪酸，但是全球气候的变化和环境污染使得这一路径暴露出很多问题，已无法满足社会对该功能营养物质日益增多的需求。当前生物化工技术快速发展的背景，为人们寻求这一问题的解决之道开辟了新思路^[2]。

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