【作者】 丁春明；

【导师】 贺银凤；

【作者基本信息】 内蒙古农业大学 ， 农产品加工及贮藏工程， 2007， 硕士

【摘要】 本文对分离自牧民家庭酸马奶酒样品中的18株酵母菌进行高产乳糖分解酶的酵母菌菌株筛选,在同容量牛乳中接入相同比例酵母菌(1%),培养48h,在接种前测量原乳中的乳糖含量及pH值,在接种后12h,24h,48h测量接入酵母菌牛乳中的乳糖含量及pH值,由实验数据比较接入不同菌株的牛乳中乳糖变化量及PH值,从中筛选出1株产乳糖酶量高的菌株(J20-3)。测得接入酵母菌J20-3前牛乳中乳糖含量为59.69mg/mL,接入后12后变为17.64 mg/mL,为接种前29.55%;24h变为1.87 mg/mL,为接种前3.13%,24h后乳糖量基本不再变化。在此基础上,对酵母菌(J20-3)培养基组成成分乳糖、酵母汁、蛋白胨比例依据二次相应曲面法(Box-Behnken)优化,设计了三因素三水平的响应面分析(RSA)试验,共有15个试验点。优化结果为1000mL酵母菌培养基中乳糖为18.31g,酵母汁为5.23g,蛋白胨为10.43g。利用优化过的培养基培养酵母菌J20-3,参照中性乳糖酶的测定方法—吉斯特·布洛卡兹法测定粗酶液中酶活力。定在37℃,pH为7.3的条件下测定其单位菌体干重量所含乳糖酶,作为判别其乳糖酶活力的一个客观指标。测得单位重量酵母菌的乳糖酶含量:23.11IU/g。连续培养酵母菌J20-324h,每隔2h测量其菌体干重,以logistic模型为基础,建立该酵母菌在30℃下,菌体干重关于时间的生长模型。由试验数据确定模型参数:Cm=1.04kg/m3,Co=0.32kg/m3。将试验数据代入LN(Cm/C0-1)+LN[Cx/(Cm-Cx)]并对时间t作图,得到:斜率为k=0.194,截距intercept=0.04.最后建立方程: Cx=0.32*EXP(0.04+0.194*t)/(1-(0.32/1.04)*(1-EXP(0.04+0.194*t)))。实验数据与理论值相对误差在5%左右,模型拟和较好。更多还原

【Abstract】 The paper studied the screening of the yeast with high vitalisticβ-Glycosidase, 18 strains of yeasts isolated from herdsman-made koumiss were used. The same proportion of yeast (1%) was inoculated into the milk with the same volume, and cultivated for 48h. The measurements of lactose content and pH value were made respectively before cultivation and in 12h, 24 hand 48h after cultivation. By comparison of the changes in lactose content and pH values, one strain with high vitalisticβ-Glycosidase was screened out, named as J20-3. The lactose content of the milk was 59.69mg/mL before inoculation, and it changed to 17.64mg/mL in 12h after inoculation, accounted for 29.55% of that before inoculation; it changed to 1.87mg/mL in 24h after inoculation, accounted for 3.13% of that before inoculation. After 24h, the lactose content did not change nearly. Based on the tests, the constitution of moiety medium, lactose, yeast juice and peptone were optimized by Box-Behnken method, three-factor and three levels Response Surface Methodology was designed and 15 experiment points were gotten. The optimization results were 18.31g for lactose, 5.23g for yeast juice and 10.43g for peptone in the 1000ml moiety medium. The enzyme activity of crude enzyme was determined by Gist & Brocades method. The activity ofβ-Galactosidase were decided by content ofβ-Galactosidase at 37℃and pH of 7.3 per thalline dry weight,and the content was 23.11IU/g. The thalline dry weight was detected every 2 hours after yeasts J20-3 cultivation within 24 hours at 30℃. The thalline dry weight vs. time referred to Logistic model was used. The parameter Cm=1.04kg/m3, Co=0.32kg/m3 were got. Experimental data were plot LN (Cm/C0-1) +LN [Cx/ (Cm-Cx)] vs. time. The slope was K=0.194, the intercept=0.04. The modelCx=0.32*EXP (0.04+0.194*t)/ {1-[0.32/1.04-EXP (0.04+0.194*t)]} was definited. As the proportional error between experimental data and theoretical value was about 5%, the model was fit.更多还原