甜菊糖是一类天然、非营养、功能性高倍甜味剂,被称为世界第3糖原。斯替夫苷是甜菊糖的主要甜味成分,其分子结构中含有3个可供水解的糖苷键。专一性水解斯替夫苷的糖苷键可以得到甜度和性能各异的功能性糖苷。文章发现了1种来源于黑曲霉(Aspergillus niger)的脂肪酶Lip A能特异性水解斯替夫苷,是首次被发现的可催化水解斯替夫苷的脂肪酶。该研究采用单因素优化的方法,依次探究温度、pH、底物浓度、加酶量、金属离子等因素对酶促反应的影响,并对反应路径进行初步解析。实验结果表明,脂肪酶Lip A对斯替夫苷具有高特异性,主要水解产物为甜茶苷。在55 ℃,pH 4.5,加酶量为1 200 U/g 环境下,反应9 h斯替夫苷转化率可达99%,甜茶苷产率为90%。该研究扩充了甜茶苷的制备方法,对甜菊糖苷的深度应用具有重要的意义。
Steviol glycosides are a natural, non-nutritive, high-intensity sweetener with functional properties, known as the world’s third sugar source.Stevioside is the main sweetening component of Steviol glycosides, with its molecular structure containing three glycosidic bonds available for hydrolysis.The specific hydrolysis of the glycosidic bond in stevioside can yield functional glycosides with varying sweetness and properties.This article first discovered that lipase A from Aspergillus niger can specifically hydrolyze stevioside to prepare rubusoside.This study investigated the effects of factors such as temperature, pH, substrate concentration, enzyme dosage, metal ions, etc., on the enzymatic reaction with a single-factor optimization method, and conducted a preliminary analysis of the reaction pathway.Results indicated that lipase A exhibited high specificity towards stevioside, with the main hydrolysis product being rubusoside.Under the optimal conditions of 55 ℃, pH 4.5, and an enzyme dosage of 1 200 U/g, the conversion rate of stevioside could reach 99% after a 9-hour reaction, with a rubusoside yield of 90%.This study expanded the preparation methods of rubusoside, which is of significant importance for the in-depth application of stevia glycosides.
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