初始过饱和度对谷氨酸结晶的影响研究  

Effects of Initial Super-saturation on the Polymorphism and Size Distribution of Glutamic Acid

作　　者：张建华[1] 曹付明[1] 张宏建[1] 唐蕾[1] 毛忠贵[1] 

机构地区：[1]江南大学生物工程学院工业生物技术教育部重点实验室,江苏无锡214122

出　　处：《高校化学工程学报》2013年第1期43-49,共7页Journal of Chemical Engineering of Chinese Universities

基　　金：国家863高技术研究与发展计划项目(2006AA020303-02)

摘　　要：以谷氨酸一钠(MSG)水溶液模拟发酵液,采用pH-shift模式研究溶液初始过饱和度对谷氨酸结晶的影响。结果表明:过饱和度同时影响谷氨酸结晶的晶习和粒度分布。当过饱和度S≤7.15时,谷氨酸主要以α型晶习析出,粒径呈对数对称分布。随着过饱和度增大,β型结晶比例增大,中位径趋小且粒度分布范围变宽。当S≥14.17以后,晶体全部是β型晶习,晶体粒度分布分散且无规律。根据经典成核理论计算了不同过饱和度/MSG浓度时两种谷氨酸晶习的成核速率,证明两种晶习的成核速率均随过饱和度增加而加快,相同过饱和度时α型晶习成核速率大于β型,而相同MSG浓度时β型成核速率大于α型。研究认为,结晶成核速率随过饱和度增大而加快是影响谷氨酸结晶粒度分布的主要原因,而晶体晶习主要取决于α、β型两种晶核的竞争性成核速率的差值。基于已有研究报道及实验结果,提出了α和β型谷氨酸晶体的C-pH相图模型,解释了过饱和度影响谷氨酸结晶晶习的规律。The effect of initial glutamic acid（GA） super-saturation on GA crystallization was investigated by using monosodium glutamate（MSG） solution to replace GA fermentation broth under pH-shift operation mode.The results show that the super-saturation degree of the solution influences both crystal habit and crystal size distribution（CSD）.The crystal habit is mainly in α-form and CSD exhibits a symmetric distribution with logarithmic form when super-saturation degree（S） is below 7.15（S≤7.15）.With the increase of super-saturation degree,the β-form crystal percentage increases and medium size crystallization decreases but with a wider CSD.When S exceedes 14.17（S≥14.17）,all of the crystal habit are in β-form,and CSD becomes dispersive and irregular.Based on the classical nucleation theory,the GA polymorphism nucleation rates under different super-saturation degrees and MSG concentrations are calculated,and the results demonstrates that the polymorphism nucleation rates both increase with the increases of super-saturation degree and MSG concentration.The α-form crystal nucleation rate is faster than that of β-form at the same super-saturation degree,while β-form crystal nucleation rate is faster than that of α-form at the same MSG concentration.The results suggest that the major reason accounting for CSD of glutamic acid is due to the nucleation rate increases with the increase of super-saturation degree,while the crystal habit mainly depends on the difference of the two competitive nucleation rates.A C-pH phase diagram model for α-and β-GA crystals was proposed based on the existing reports and the results obtained in this study,and this model could theoretically interpret the mechanism of super-saturation degree affecting GA crystal habit.

关 键 词：谷氨酸 结晶 过饱和度 晶习 粒度分布 

分 类 号：TQ922.1[轻工技术与工程—发酵工程]