Enzymatic biosensor has been paid much attention to the research fields due to its advantage in medical application. As one of the application, we determined the optimum value of cholesterol oxidase against cholesterol. In this work, we studied the behavior of cholesterol oxidation by enzymatic reaction to get the optimum condition for cholesterol oxidation. The enzyme that used were in two form, free cholesterol oxidase, and immobilized cholesterol oxidase. Cholesterol oxidase was produced from Streptomyces sp. by using solid state fermentation method and identified had high enzyme activity to be 5.12 U/mL. Cholesterol oxidase was simultaneously crosslinked immobilized onto magnetite coated by silicon dioxide (M-SiO2). The support was characterized by Fourier transform infrared (FTIR) to determine the functional group of modified particle and scanning electron microscope (SEM) to observe the morphological or our prepared particle. Cholesterol oxidase sensitivity to substrate was analyzed by using HPLC with different interval time measurements. The oxidation of cholesterol by free enzyme and immobilized enzyme was also investigated. The best sensitivity of cholesterol oxidase was estimated to oxidize Cso (concentration of substrate) 1.46 mM of substrate with Ce (concentration of enzyme) 20 mg/mL for 180 min. Final oxidation value of cholesterol by immobilized enzyme was greater than 60%. The results of this study revealed that immobilized enzyme for cholesterol oxidation was stable, reproducible, and sensitive.

中文翻译：

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链霉菌属的胆固醇氧化酶的固定化 交联法制备磁铁矿二氧化硅的研究

酶生物传感器由于其在医学应用中的优势而备受关注。作为应用之一，我们确定了针对胆固醇的胆固醇氧化酶的最佳值。在这项工作中，我们通过酶促反应研究了胆固醇氧化的行为，从而获得了胆固醇氧化的最佳条件。使用的酶有两种形式：游离胆固醇氧化酶和固定化胆固醇氧化酶。胆固醇氧化酶由链霉菌属产生。通过固态发酵法，经鉴定具有较高的酶活性为5.12 U / mL。同时将胆固醇氧化酶交联固定在涂覆有二氧化硅（M-SiO 2）的磁铁矿上。通过傅里叶变换红外（FTIR）确定改性颗粒的官能团，并通过扫描电子显微镜（SEM）观察载体或制备的颗粒，对载体进行了表征。使用不同间隔时间测量的HPLC分析胆固醇氧化酶对底物的敏感性。还研究了游离酶和固定化酶对胆固醇的氧化作用。估计胆固醇氧化酶的最佳敏感性是用20 mg / mL的Ce（酶的浓度）氧化Cso（底物的浓度）1.46 mM的底物，持续180分钟。固定化酶最终胆固醇的氧化值大于60％。这项研究的结果表明，固定化的胆固醇氧化酶稳定，可重复且敏感。