Aghaei Hamidreza, Ghavi Maryam, Hashemkhani Ghazaleh, Keshavarz Morteza
Department of Chemistry, Shahreza Branch, Islamic Azad University, P.O. Box 311-86145, Shahreza, Isfahan, Iran.
Department of Chemistry, Shahreza Branch, Islamic Azad University, P.O. Box 311-86145, Shahreza, Isfahan, Iran.
Int J Biol Macromol. 2020 Nov 1;162:74-83. doi: 10.1016/j.ijbiomac.2020.06.145. Epub 2020 Jun 18.
In this study, two synthetic layered doubled hydroxides (LDH), including Mg/Al-CO-LDH (LDH1) and Zn/Al-CO-LDH (LDH2), were prepared using the co-precipitation method and modified with sodium dodecyl sulfate to be utilized as carriers for immobilization of Candida rugosa lipase via the adsorption. The activity of prepared biocatalysts was measured in the olive oil hydrolysis. The effects of lipase concentration, pH, storage stability and thermal resistance of the samples were also studied. The maximum activity was obtained at pH 6.0 for immobilized lipase on modified LDHs with monolayer surfactants, including MLDH1 (0.922 U/mg) and MLDH2 (0.744 U/mg), respectively. The remained activities for immobilized lipase on MLDH1 and MLDH2 after 24 h incubation at 60 °C were 85% and 81%, respectively. During the 25days of storage at 4 °C, immobilized lipases on MLDH1, MLDH2, and free lipase kept 87%, 86%, and 70% of their initial activities. The residual activities for immobilized lipase on MLDH1 and MLDH2 after reusing for ten cycles were 72% and 67% of their initial activities. Adsorption parameters for sorption of lipase on all supports were fitted to the Freundlich and Langmuir isotherms. Kinetic parameters obtained from the Michaelis-Menten equation on MLDH1 and MLDH2 were comparable to free enzyme.
在本研究中，采用共沉淀法制备了两种合成层状双氢氧化物（LDH），即Mg/Al-CO-LDH（LDH1）和Zn/Al-CO-LDH（LDH2），并用十二烷基硫酸钠进行改性，以用作通过吸附固定化皱褶假丝酵母脂肪酶的载体。在橄榄油水解反应中测定了所制备生物催化剂的活性。还研究了样品中脂肪酶浓度、pH值、储存稳定性和耐热性的影响。对于用单层表面活性剂改性的LDH固定化脂肪酶，在pH 6.0时分别获得了最大活性，其中MLDH1（0.922 U/mg）和MLDH2（0.744 U/mg）。在60℃孵育24小时后，MLDH1和MLDH2上固定化脂肪酶的剩余活性分别为85%和81%。在4℃储存25天期间，MLDH1、MLDH2上的固定化脂肪酶和游离脂肪酶分别保持其初始活性的87%、86%和70%。重复使用十次后，MLDH1和MLDH2上固定化脂肪酶的残余活性分别为其初始活性的72%和67%。脂肪酶在所有载体上的吸附参数符合Freundlich和Langmuir等温线。从Michaelis-Menten方程获得的MLDH1和MLDH2的动力学参数与游离酶相当。
