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A modelling study on hydrolysis of whey lactose and stability of β-galactosidase
Belma Özbek,Elçin Demirhan,Dilek K l ç Apar 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.2
In the present study, the effect of process conditions on whey lactose hydrolysis and enzyme inactivation were investigated. The experiments were carried out in 250 mL of 25 mM phosphate buffer solution by using β-galactosidase produced from Kluyveromyces marxianus lactis in a batch reactor system. The degree of lactose hydrolysis (%) and residual enzyme activity (%) against time were investigated versus lactose concentration, enzyme concentration,temperature and pH. The mathematical models were derived from the experimental data to show the effect of process conditions on lactose hydrolysis and residual enzyme activity (in the presence and absence of lactose). At the optimum process conditions obtained (50 g/L of lactose concentration, 1 mL/L of enzyme concentration, 37 oC of temperature and pH 6.5), 81% of lactose was hydrolyzed and enzyme lost its activity by 32%. The activation energy for hydrolysis reaction (EA) and the enzymatic inactivation energy (ED) were calculated as 52.7 kJ/mol and 96.7 kJ/mol. Mathematical models at various process conditions have been confirmed with the experimental results.
Elçin Demirhan,Belma Özbek,Dilek K l ç Apar 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.1
We investigated the effects of process parameters (substrate concentration, enzyme concentration, temperature and pH) on the hydrolysis and solubilization of sesame cake protein as well as enzyme stability. The sesame cake protein was hydrolyzed by Alcalase enzyme (a bacterial protease produced by a selected strain of Bacillus Licheniformis)that was chosen among five commercial enzymes examined. The optimum process conditions for hydrolysis and solubilization were obtained as 15 g L^(−1) substrate concentration, 3 ml L^(−1) enzyme concentration, 50 ℃ and pH 8.5. Under these conditions, the values of degree of hydrolysis and solubilization were found as 26.3% and 82.1%, respectively,and enzyme lost its activity by approx. 56% at the end of 120 min processing time. Modeling studies were performed to determine the kinetics of hydrolysis, solubilization and enzyme inactivation. The relationship between hydrolysis and solubilization was found linear for all experimental conditions examined. The inactivation energy of Alcalase at the temperature range of 45-55 ℃ was determined to be 25544 J mol^(−1).