Optimization of physical immobilization of lipase enzyme on halloysite nanotubes using Response Surface Methodology and investigating the multiple usability of immobilized enzyme

Lipases are key enzymes for the hydrolysis of triglycerides in different food and pharmaceutical industries, but limitations such as low stability, lack of reuse and high costs have led to a reduction in the efficiency of their use. Enzyme immobilization is one of the effective methods to overcome these limitations and, along with increasing the stability of the enzyme, makes it possible to reuse it. Several methods exist (by creating covalent bonds, entrapment, physical adsorption, etc.) to immobilize enzymes on different nano supports. One of these methods is the enzyme immobilization by physical absorption method, which has several advantages such as the non-use of chemical compounds. In recent years. The use of nanotubes advantages such as the non-use of chemical compounds. In recent years. The use of nanotubes has been proposed to immobilize the enzyme by providing more surfaces for enzyme adsorption, availability, non-toxicity and ease of use, In this study, the effective parameters for the physical immobilization of lipase enzyme on halloysite nanotubes were optimized using RSM. Independent parameters included the amount of halloysite (5-20 mg), initial enzyme concentration (30-30 μg/ml), immobilization time (30-300 minutes) and temperature (5-35 C). The effects of these parameters on immobilization efficiency and enzyme activity was studied. Quadratic equations were used to explain the relationship between independent parameters and responses. The coefficient of determination and the adjusted coefficient of the values for the enzyme immobilization efficiency were 0.92 and 0.9 and for the specific activity of the enzyme were 0.99 and 0.98, respectively. The amount of hallovsite 50 to 80 mg, lipase enzyme concentration 30 to 57 μg/ml, temperature and immobilization time, were determined as 20 C and 165 minutes, respectively. The enzyme activity and immobilization efficiency were 1500 U/gr and 70% respectively, in optimum conditions. Enzyme activity was measured in optimal conditions up to 10 cycles. The results showd that the enzyme retained its activity after 10 cycles to 87.83%. from this study, it can be concluded that enzyme immobilization is one of the effective methods for increasing the usability of enzymes several times, which can greatly reduce the cost of production in the industry.