本文選題：乳酸菌　切入點：重離子輻照　出處：《甘肅農(nóng)業(yè)大學(xué)》2017年碩士論文

【摘要】：乳酸菌是一種能夠在發(fā)酵過程中利用葡萄糖或乳糖產(chǎn)生乳酸的細(xì)菌,它能夠給機(jī)體提供所需的營養(yǎng)物質(zhì),同時能夠調(diào)節(jié)機(jī)體胃腸道正常菌群的平衡,調(diào)節(jié)增強(qiáng)機(jī)體免疫力。乳酸菌的一個重要特性是菌體的發(fā)酵產(chǎn)酸能力。高產(chǎn)酸的乳酸菌在乳酸菌制品生產(chǎn)過程中較普通乳酸菌可以縮短發(fā)酵時間,提高生產(chǎn)效率,從而降低生產(chǎn)成本,提高經(jīng)濟(jì)效益。因此,篩選具有優(yōu)良性能的乳酸菌,研究乳酸菌的生長特性對于乳酸菌制品的工業(yè)化生產(chǎn)有著積極的意義。本試驗以植物乳酸菌株(Lactobacillus plantarum JT)為出發(fā)菌株,對其進(jìn)行重離子輻照誘變,通過篩選平板初篩和試管發(fā)酵復(fù)篩的方法選育得到最終的高產(chǎn)酸突變?nèi)樗峋�。同時通過優(yōu)化高產(chǎn)菌株發(fā)酵條件,來提高乳酸突變菌株的產(chǎn)酸能力。本試驗為微生物菌種選育提供新的方法,為乳酸菌的工業(yè)化利用奠定理論基礎(chǔ)。本試驗的研究結(jié)果如下:1、植物乳酸菌出發(fā)菌株JT進(jìn)行重離子束輻照誘變,篩選得到高產(chǎn)酸突變菌株JT10,突變菌株發(fā)酵產(chǎn)乳酸量為21.72 g/L,與原始菌株JT的產(chǎn)酸量(15.12 g/L)相比提高了43.65%(P0.001);同時,通過對突變菌株JT10的傳代穩(wěn)定性研究,結(jié)果顯示JT10菌株具有良好的產(chǎn)酸遺傳穩(wěn)定性。2、通過進(jìn)一步篩選最終獲得5株高產(chǎn)突變菌株JT6、JT7、JT8、T9、JT10,連續(xù)傳代9次其乳酸產(chǎn)量均具有良好的遺傳穩(wěn)定性,產(chǎn)酸最高的JT10菌株與原始菌株的乳酸產(chǎn)量相比提高了43.78%,具有極顯著性差異(P0.001)。3、通過對篩選得到的突變?nèi)樗峋闖T10的產(chǎn)乳酸發(fā)酵條件的優(yōu)化研究,得到該菌株的最佳發(fā)酵條件是:種子液培養(yǎng)時間為16 h,發(fā)酵液培養(yǎng)時間為22 h,轉(zhuǎn)接時的接種量為5%,初始pH值為7,培養(yǎng)溫度為37℃;結(jié)果顯示在最佳發(fā)酵條件下得到的乳酸菌產(chǎn)酸量(24.07 g/L)與突變高產(chǎn)菌株JT10在原始發(fā)酵條件下的產(chǎn)酸含量(21.72g/L)相比提高了10.82%(P0.01)。本試驗建立了重離子輻照誘變后選育乳酸高產(chǎn)菌株的篩選方法,并應(yīng)用該方法選育得到高產(chǎn)乳酸菌突變菌株JT10,經(jīng)過發(fā)酵條件優(yōu)化,最終使乳酸菌的產(chǎn)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，

本文編號：1656796