CAJ | 학술논문

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.
이곡안산일납(MSG)수용액모의발효액,채용 pH-shift 모식연구용액초시과포화도대곡안산결정적영향.결과표명:과포화도동시영향곡안산결정적정습화립도분포.당과포화도S≤7.15시,곡안산주요이α형정습석출,립경정대수대칭분포.수착과포화도증대,β형결정비례증대,중위경추소차립도분포범위변관.당 S≥14.17이후,정체전부시 β형정습,정체립도분포분산차무규률.근거경전성핵이론계산료불동과포화도/MSG 농도시량충곡안산정습적성핵속솔,증명량충정습적성핵속솔균수과포화도증가이가쾌,상동과포화도시α형정습성핵속솔대우β형,이상동 MSG 농도시β형성핵속솔대우α형.연구인위,결정성핵속솔수과포화도증대이가쾌시영향곡안산결정립도분포적주요원인,이정체정습주요취결우α、β형량충정핵적경쟁성성핵속솔적차치.기우이유연구보도급실험결과,제출료α화β형곡안산정체적C-pH상도모형,해석료과포화도영향곡안산결정정습적규률.
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, theβ-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, whileβ-form crystal nucleation rate is faster than that ofα-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 forα-andβ-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.