论文总字数：17843字

摘 要

在乙醇发酵生产过程中，代谢产物及环境条件会抑制酵母生长及发酵能力，从而大大降低了发酵效率。本实验室通过低温等离子体技术诱变，选育得到了一株抗冻酵母Saccharomyces cerevisiae AFY-1。固定化技术可改善酵母对代谢产物和环境的耐受性，提高乙醇产量。本论文以游离和固定化原始酵母、游离和固定化抗冻酵母为材料进行乙醇发酵，通过单因素实验比较游离和固定化原始酵母、游离和固定化抗冻酵母AFY-1的发酵能力和发酵稳定性，探究固定化抗冻酵母AFY-1的重复使用稳定性。结果表明，在不同的发酵条件下，抗冻酵母AFY-1的发酵能力优于原始酵母。固定化能够进一步提高抗冻酵母AFY-1对糖和温度的发酵稳定性。固定化抗冻酵母AFY-1在普通培养基中使用1～5次，最终乙醇收率和残糖浓度分别在21.5%、30.2 g/L基本不变；在高糖高酸培养基中，第1次使用时的乙醇收率和残糖浓度分别为20.3%、90.3 g/L，第5次使用时的乙醇收率和残糖浓度分别为15.3%、185.0 g/L。

关键词： 固定化 酵母 乙醇 发酵 稳定性

Analysis of Ethanol Fermentation Performance

of Immobilized Freeze-tolerant Yeast AFY-1

Abstract

In the process of ethanol fermentation, the metabolites and environment conditions might inhibit the growth and fermentation ability of yeast, thus greatly reduce the efficiency of fermentation. Our laboratory has developed a freeze-tolerant yeast strain Saccharomyces cerevisiae AFY-1. Immobilization can improve the tolerance of yeast to metabolites and environment conditions, and increase alcohol production. In the present study, free and immobilized freeze-tolerant yeast AFY-1, and free and immobilized parent yeast were used for fermentation. The fermentation stabilities of free and immobilized freeze-tolerant yeast AFY-1, and free and immobilized parent yeast under different conditions of sugar, alcohol, acid and temperature were compared. The reuse stability of immobilized freeze-tolerant yeast AFY-1 was also discussed. It was shown that the fermentation ability of freeze-tolerant yeast AFY-1 was better than that of parent yeast under different fermentation conditions. The immobilization further improved the fermentation ability of freeze-tolerant yeast AFY-1, and its fermentation stability against the change of sugar concentration and temperature. During the reuse of immobilized freeze-tolerant yeast AFY-1 in the ordinary culture medium for 1 to 5 times, the final ethanol yield and residual sugar concentration were basically constant at 21.5% and 30.2 g/L, respectively. In culture medium with high glucose and high acid concentration, the final ethanol yield and the residual sugar concentration were 20.3% and 90.3 g/L respectively at the first use, and 15.3 % and 185.0 g/L respectively at the fifth use.

Key Words: Immobilization; Yeast; Alcohol; Fermentation; Stability

目 录

摘 要 I

Abstract II

第一章 文献综述 1

1.1 细胞固定化技术 1

1.2 抗冻酵母 2

1.3 酵母对环境因素的耐受性 2

1.3.1 酵母对高糖的耐性 2

1.3.2 酵母对乙醇的耐性 3

1.3.3 酵母对酸的耐性 3

1.3.4 酵母对温度的耐性 3

1.4 本课题的研究目的及意义 3

第二章 实验材料与方法 4

2.1 实验材料 4

2.2 酵母培养 4

2.3 酵母固定化 5

2.4 乙醇发酵 5

2.5 糖和乙醇浓度测定 5

2.6 细胞数测定 6

2.6.1 游离酵母的细胞数测定 6

2.6.2 固定化酵母的细胞数测定 6

第三章 结果与讨论 8

3.1 对糖的发酵稳定性 8

3.2 对乙醇的发酵稳定性 10

3.3 对酸的发酵稳定性 13

3.4 对温度的发酵稳定性 16

3.5 乙醇收率与总细胞数的关系 18

3.6 重复使用稳定性 19

第四章 结论与展望 24

4.1 结论 24

4.2 展望 24

参考文献 25

致 谢 27

第一章 文献综述

1.1 细胞固定化技术

细胞固定化技术是近现代以来出现的一种新型生物技术，即是指利用物理或化学手段将游离的微生物细胞定位于限定的空间区域，并使其保持活性和可反复使用的一种新型生物技术^[1-3]。固定化细胞保持了细胞的生命活动能力，比游离细胞及固定化酶有更大的优势^[4]。

和游离细胞相比，固定化细胞提供了很多优势：高细胞密度或高细胞负载量，提高了单位体积的产量，缩短了反应时间，减小了反应器的型号，从而降低了成本费用，由于固定化细胞的稳定再生从而可以长时间的重复利用，形成连续过程后可提高洗脱率，进而降低损失，提高底物利用率，降低污染微生物的几率，简化过程设计，提高细胞对产物及环境的耐性^[5]。

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