【作者】 周涛；

【导师】 毛忠贵；

【作者基本信息】 江南大学 ， 环境工程， 2004， 硕士

【摘要】 本论文对等电母液中谷氨酸的提取进行了研究。首先对谷氨酸等电母液中的菌体去除进行了研究。结果表明,选用聚丙烯酸钠作为絮凝剂,加入量2%,温度60℃,pH3.6,搅拌转速20r/min时,搅拌15min,菌体去除率在90%以上。其次以谷氨酸菌体蛋白为原料,经过稀酸预处理后,用蛋白酶水解得到复合氨基酸水解液。通过正交实验,确定酶解最佳条件:酶加量400U/g,温度为40℃,pH7.5,水解时间12h,底物浓度比为1:30。在此条件下,测得菌体蛋白水解率为72.4%。再次,确定了脱盐的最佳工艺流程,并对谷氨酸的二次等电结晶进行探索。实验表明,谷氨酸二次等电结晶的收率为70%以上。另外,本文测定了在四种体系内,即纯水、1%NH4+浓度溶液、0.1%菌体溶液及实际工业发酵液体系谷氨酸的溶解度和超溶解度曲线。将这些曲线用数学表达式拟合,可计算出谷氨酸等电点时的介稳区宽度。实验结果表明,介稳区宽度在纯水、0.1%菌体溶液、1%NH4+浓度溶液及实际工业发酵液内逐渐变窄,即谷氨酸在这些体系内的溶解度逐渐变大,其拟合的饱和度和超饱和度曲线具有以下形式:。本文测定了谷氨酸溶液于不同降温速率、搅拌转速下的结晶介稳区宽度以及不同过饱和度下的晶体生长速度和结晶成核诱导期。实验结果显示,谷氨酸的结晶介稳区随降温速率的增加而变宽,随搅拌转速的增加而变窄。晶体生长速率随相对过饱和度增加而增加,而结晶成核诱导期随相对过饱和度的增加而缩短。更多还原

【Abstract】 This paper studied the glutamic acid extraction in the isoelectric point mother solution. Firstly, bacteria removal in the glutamic acid isoelectric point mother solution was studied. Polyacrylate sodium was used as the flocculation agent. The experimental results showed that the optimum conditions were as follows: polyacrylate sodium 2%, pH 3.6, temperature 60℃, stirring speed 20r/min and stirring time 15min.The removal rate of the bacteria was above 90%. Then, glutamic acid thalli was treated with diluted acid and hydrolyzed by protease to obtain amino acid hydrolysate. The optimal hydrolytic conditions were determined by orthogonal test: the protease amount ,400U/g; temperature, 40℃; pH ,7.5; hydrolytic time, 12 hours; and substrate concentration ,1:30. The protein hydrolysis yield was 72.4% under these conditions. The optimum desalination process was determined, and the second isoelectric point crystallization. was also studied. The extraction yield of glutamic acid was above 70%. The solubility and supersolubility curves for glutamic acid crystallization in pure water, solutions containing 0.1% bacteria, and 1% NH4+, and practical industrial fermentation broth were measured experimentally. By fitting these curves mathematically, the widths of the metastable zones for glutamic acid in these four systems were calculated. The experimental results showed that the widths of the metastable zones decreased gradually in the systems of pure water, solutions of 0.1% bacteria, and 1% NH4+, and practical industrial fermentation broth, which means the solubility in these systems increases in the same sequences. The solubility and supersolubility curves had the following common mathematical formula:.The metastable zone widths of glutamic acid solution at different cooling, agitation, and crystallization growth rates, as well as the induction periods of crystallization nucleation under different supersaturations were measured. The experimental results showed that glutamic acid solubility increases moderately with the increase of temperature, the metastable zone width increases with the increase of the cooling rate and decreases with the increase of agitating rate. The crystallization growth rate of glutamic acid increases and the induction period decreases with the increase of supersaturation.更多还原