title: Immobilization of Aspergillus oryzae  β-Galactosidase on Cellulose Acetate-Polymethylmethacrylate Membrane and Its Application in Hydrolysis of Lactose from Milk and Whey.
abstract: The present study demonstrates the immobilization of Aspergillus oryzae β-galactosidase on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane and its application in hydrolyzing lactose in dairy industries. The effect of physical and chemical denaturants like pH, temperature, product inhibition by galactose, storage stability, and reuse number of the enzyme immobilized on CA-PMMA membrane has been investigated. Lactose was hydrolyzed from milk and whey in batch reactors at 50°C by free and immobilized β-galactosidase (IβG). Optimum pH for the free and immobilized enzyme was found to be the same, that is, 4.5. However, IβG retained greater fractions of catalytic activity at lower and higher pH ranges. The temperature optimum for the immobilized enzyme was increased by 10°C. Moreover, Michaelis-Menten constant was increased for IβG as compared to the native one while maximum reaction rate was reduced for the immobilized enzyme. The preserved activity of free and immobilized enzyme was found to be 45% and 83%, respectively, after five weeks of storage at 4°C. Reusability of IβG was observed to be 86% even after fifth repeated use, thereby signifying its application in lactose hydrolysis (as shown in lab-scale batch reactors) in various dairy products including milk and whey.
authors.affiliation: Center of Excellence in Genomic and Medicine Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Shakeel Ahmed
authors.initials: SA
authors.lastname: Ansari
authors.affiliation: Department of Biochemistry, Ibn Sina National College for Medical Sciences, Jeddah 21418, Saudi Arabia.
authors.forename: Rukhsana
authors.initials: R
authors.lastname: Satar
authors.affiliation: Center of Excellence in Genomic and Medicine Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Syed
authors.initials: S
authors.lastname: Kashif Zaidi
authors.affiliation: Environmental Biotechnology Division, CSIR-Indian Institute of Toxicology Research, M.G. Marg, Lucknow 226001, India.
authors.forename: Abrar
authors.initials: A
authors.lastname: Ahmad