College of Food and Biology Engineering, Jimei University, Xiamen, China.
Fujian Provincial Key Laboratory of Food Microbiology and Enzyme Engineering, Xiamen, China.
J Food Biochem. 2022 Feb;46(2):e14055. doi: 10.1111/jfbc.14055. Epub 2021 Dec 30.
In this study, we found the addition of sorbitol could improve the thermostability of α-l-rhamnosidase from Aspergillus niger. When α-l-rhamnosidase with sorbitol was heat-treated at 60°C, 65°C, and 70°C, the half-life t increased by 28-, 18-, and 9-fold, respectively. Inactivation thermodynamic analysis showed that both E and ΔG of α-l-rhamnosidase increased. Through the response surface methodology (RSM) analysis, the higher hesperidin conversion (63.26%) by α-l-rhamnosidase was attained with 0.7 M sorbitol at 60°C and pH 4.5 for 10 min. Furthermore, hesperidin could be completely hydrolyzed after 10 hr of reaction. Overall, the results indicated that the addition of sorbitol improved the thermostability of α-l-rhamnosidase and increased the enzymatic conversion of hesperidin to hesperetin-7-O-glucoside (HMG). It also provided a simple and efficient way to increase enzymatic conversion of other valuable flavonoid monomers due to the broad substrate specificities of α-l-rhamnosidase from A. niger. PRACTICAL APPLICATIONS: Hesperetin-7-O-glucoside (HMG), a derhamnosylation product of hesperidin, is considered as a synthetic precursor for novel and efficient sweeteners and is important in food, functional food, and nutraceutical industries. Compared to chemical hydrolysis methods, the enzymatic conversion of hesperidin is milder and has the advantages of high specificity. Adding sorbitol can improve the thermostability of α-l-rhamnosidase and increase the enzyme efficacy against hesperidin. This study gave more evidence that adding sorbitol could improve the thermostability of enzymes and provide a better choice for improving biotransformation potency of enzymes.
在这项研究中，我们发现添加山梨醇可以提高黑曲霉α-l-鼠李糖苷酶的热稳定性。当α-l-鼠李糖苷酶与山梨醇一起在 60°C、65°C 和 70°C 下热处理时，半衰期 t 分别延长了 28、18 和 9 倍。失活动力学分析表明，α-l-鼠李糖苷酶的 E 和ΔG 均增加。通过响应面法（RSM）分析，α-l-鼠李糖苷酶在 0.7 M 山梨醇、60°C 和 pH 4.5 下反应 10 分钟时，可获得较高的柚皮苷转化率（63.26%）。此外，经过 10 小时的反应，柚皮苷可完全水解。总体而言，结果表明添加山梨醇可提高α-l-鼠李糖苷酶的热稳定性，增加柚皮苷转化为柚皮素-7-O-葡萄糖苷（HMG）的酶促转化率。由于黑曲霉α-l-鼠李糖苷酶具有广泛的底物特异性，它还为提高其他有价值的类黄酮单体的酶促转化率提供了一种简单有效的方法。
柚皮素-7-O-葡萄糖苷（HMG）是柚皮苷去鼠李糖苷化的产物，被认为是新型高效甜味剂的合成前体，在食品、功能性食品和营养保健品行业中具有重要地位。与化学水解方法相比，柚皮苷的酶促转化更为温和，具有高特异性的优点。添加山梨醇可以提高α-l-鼠李糖苷酶的热稳定性，增加酶对柚皮苷的酶效。本研究为添加山梨醇可以提高酶的热稳定性，为提高酶的生物转化能力提供了更好的选择提供了更多证据。
