重离子辐照诱变选育高产酸乳酸菌株及其发酵条件优化研究

发布时间：2018-03-24 05:02

  本文选题：乳酸菌　切入点：重离子辐照　出处：《甘肃农业大学》2017年硕士论文

【摘要】：乳酸菌是一种能够在发酵过程中利用葡萄糖或乳糖产生乳酸的细菌,它能够给机体提供所需的营养物质,同时能够调节机体胃肠道正常菌群的平衡,调节增强机体免疫力。乳酸菌的一个重要特性是菌体的发酵产酸能力。高产酸的乳酸菌在乳酸菌制品生产过程中较普通乳酸菌可以缩短发酵时间,提高生产效率,从而降低生产成本,提高经济效益。因此,筛选具有优良性能的乳酸菌,研究乳酸菌的生长特性对于乳酸菌制品的工业化生产有着积极的意义。本试验以植物乳酸菌株(Lactobacillus plantarum JT)为出发菌株,对其进行重离子辐照诱变,通过筛选平板初筛和试管发酵复筛的方法选育得到最终的高产酸突变乳酸菌株。同时通过优化高产菌株发酵条件,来提高乳酸突变菌株的产酸能力。本试验为微生物菌种选育提供新的方法,为乳酸菌的工业化利用奠定理论基础。本试验的研究结果如下:1、植物乳酸菌出发菌株JT进行重离子束辐照诱变,筛选得到高产酸突变菌株JT10,突变菌株发酵产乳酸量为21.72 g/L,与原始菌株JT的产酸量(15.12 g/L)相比提高了43.65%(P0.001);同时,通过对突变菌株JT10的传代稳定性研究,结果显示JT10菌株具有良好的产酸遗传稳定性。2、通过进一步筛选最终获得5株高产突变菌株JT6、JT7、JT8、T9、JT10,连续传代9次其乳酸产量均具有良好的遗传稳定性,产酸最高的JT10菌株与原始菌株的乳酸产量相比提高了43.78%,具有极显著性差异(P0.001)。3、通过对筛选得到的突变乳酸菌菌株JT10的产乳酸发酵条件的优化研究,得到该菌株的最佳发酵条件是:种子液培养时间为16 h,发酵液培养时间为22 h,转接时的接种量为5%,初始pH值为7,培养温度为37℃;结果显示在最佳发酵条件下得到的乳酸菌产酸量(24.07 g/L)与突变高产菌株JT10在原始发酵条件下的产酸含量(21.72g/L)相比提高了10.82%(P0.01)。本试验建立了重离子辐照诱变后选育乳酸高产菌株的筛选方法,并应用该方法选育得到高产乳酸菌突变菌株JT10,经过发酵条件优化,最终使乳酸菌的产乳酸量最大提高了59.19%。
[Abstract]:Lactic acid bacteria are bacteria that produce lactic acid by using glucose or lactose during fermentation. It provides the body with the nutrients it needs and regulates the balance of the normal flora in the gastrointestinal tract. One of the important characteristics of lactic acid bacteria is its ability to produce acid by fermentation. Lactic acid bacteria with high acid yield can shorten fermentation time and improve production efficiency compared with ordinary lactic acid bacteria in the production process of lactobacillus products. In order to reduce the production cost and improve economic efficiency, therefore, the screening of lactic acid bacteria with excellent performance, The study of the growth characteristics of lactic acid bacteria has positive significance for the industrial production of lactic acid bacteria products. In this experiment, the plant lactic acid bacteria strain Lactobacillus plantarum JT was used as the starting strain, which was induced by heavy ion irradiation. The final lactic acid strain with high acid yield was obtained by screening the plate screening method and the test tube fermentation screening method. At the same time, the fermentation conditions of the high yield strain were optimized. In order to improve the acid-producing ability of lactic acid mutant strain, this experiment provides a new method for microbial breeding. The results of this study are as follows: 1. Strain JT of plant lactic acid bacteria was induced by heavy ion beam irradiation. A mutant strain JT10 with high acid production was screened. The lactic acid production of mutant strain JT was 21.72 g / L, which was increased by 43.65g / L compared with the original strain JT (15.12 g / L). Meanwhile, the stability of the mutant strain JT10 was studied. The results showed that the JT10 strain had good acid-producing genetic stability. Through further screening, five mutant strains JT6T7, JT8, T9 and JT10 were obtained, and the lactic acid yield of JT6 strain JT7, JT8, T9 and JT10 were all of good genetic stability through further screening, and the results showed that there was good genetic stability in lactic acid yield for 9 successive passages. The lactic acid production of the JT10 strain with the highest acid production was increased by 43.78 compared with that of the original strain, and there was a significant difference (P0.001 路3). The lactic acid fermentation conditions of the mutant lactic acid bacteria strain JT10 were optimized. The optimum fermentation conditions were as follows: the culture time of seed liquid was 16 h, the culture time of fermentation liquid was 22 h, the inoculation amount was 5, the initial pH value was 7, and the culture temperature was 37 鈩，

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