Abstract：
This work explored the impact of ultrasound (US) on the activity, stability, and macrostructural conformation of cyclodextrin glycosyltransferase (CGTase) and how these changes could maximize the production of β-cyclodextrins (β-CDs). The results showed that ultrasonic pretreatment (20 kHz and 38 W/L) at pH 6.0 promoted increased enzymatic activity. Specifically, after sonication at 25 °C/30 min, there was a maximum activity increase of 93 % and 68 % when biocatalysis was carried out at 25 and 55 °C, respectively. For activity measured at 80 °C, maximum increase (31 %) was observed after sonication at 25 °C/60 min. Comparatively, US pretreatment at low pH (pH = 4.0) resulted in a lower activity increase (max. 28 %). These activation levels were maintained after 24 h of storage at 8 °C, suggesting that changes on CGTase after ultrasonic pretreatment were not transitory. These pretreatments altered the conformational structure of CGTase, revealed by an up to 11 % increase in intrinsic fluorescence intensity, and resulted in macrostructural modifications, such as a decrease in particle size and polydispersion index (up to 85 % and 45.8 %, respectively). Therefore, the sonication of CGTase under specific conditions of pH, time, and temperature (especially at pH 6.0/ 30 min/ 25 °C) promotes macrostructural changes in CGTase that induce enzyme activation and, consequently, higher production of β-CDs.
摘要：
这项工作探索了超声波（US）对活动的影响，稳定性,和环糊精糖基转移酶（CGTase）的宏观结构构象以及这些变化如何最大程度地提高β-环糊精（β-CD）的产量。结果表明，在pH6.0下超声预处理（20kHz和38W/L）促进了酶活性的提高。具体来说,在25°C/30分钟超声处理后，当在25和55°C下进行生物催化时，最大活性增加了93％和68％，分别。对于在80°C下测量的活性，在25°C/60分钟超声处理后观察到最大增加(31%)。相对而言,在低pH（pH=4.0）下进行US预处理导致较低的活性增加（最大28%）。这些活化水平在8°C储存24小时后保持。表明超声预处理后CGTase的变化不是短暂的。这些预处理改变了CGTase的构象结构，内在荧光强度增加高达11%，并导致宏观结构的改变，例如粒度和多分散指数的降低(高达85%和45.8%，分别)。因此,CGTase在特定pH条件下的超声处理，时间,和温度（尤其是在pH6.0/30分钟/25°C下）促进CGTase的宏观结构变化，从而诱导酶活化，因此,β-CD的产量更高。
