A general mathematical model for a fixed bed immobilized enzyme reactor was developed to simulate the process of diffusion and reaction inside the biocatalyst particle. The modeling and simulation of starch hydrolysis using immobilized α-amylase were used as a model for this study. Corn starch hydrolysis was carried out at a constant pH of 5.5 and temperature of . The substrate flow rate was ranging from 0.2 to 5.0？mL/min, substrate initial concentrations 1 to 100？g/L. α-amylase was immobilized on to calcium alginate hydrogel beads of 2？mm average diameter. In this work Michaelis-Menten kinetics have been considered. The effect of substrate flow rate (i.e., residence time) and initial concentration on intraparticle diffusion have been taken into consideration. The performance of the system is found to be affected by the substrate flow rate and initial concentrations. The reaction is controlled by the reaction rate. The model equation was a nonlinear second order differential equation simulated based on the experimental data for steady state condition. The simulation was achieved numerically using FINITE ELEMENTS in MATLAB software package. The simulated results give satisfactory results for substrate and product concentration profiles within the biocatalyst bead. 1. Introduction Enzyme immobilization on to supports (or carriers) and their applications as catalysts have grown considerably during the last three decades, and during the last few years have become the most exciting aspects of biotechnology [1–3]. Several methods of enzyme immobilization exist and can be classified into three main categories: carrier binding, cross linking, and entrapment [1]. A number of advantages of enzyme immobilization on to support and several major reasons are the ability to stop the reaction rapidly by removing the enzyme from the reaction solution (or vice versa), products being free of enzyme (especially useful in the food and pharmaceutical industries), reduced effluent disposal problems, suitability for continuous reactor operation, and multiple or respective use of a single batch of enzymes, especially if the enzymes are scarce or expensive, their applicability to continuous processes, and the minimization of pH and substrate-inhibition effects. This has an obvious economic impact and allows the utilization of reactors with high enzyme loads [4]. Enzyme entrapment within a gel matrix is one of the enzyme immobilization ways. In this way, the enzyme is surrounded by a semipermeable membrane. Enzyme support of a specific structure permits the contact between the
References
[1]
P. Valencia, L. Wilson, C. Aguirre, and A. Illanes, “Evaluation of the incidence of diffusional restrictions on the enzymatic reactions of hydrolysis of penicillin G and synthesis of cephalexin,” Enzyme and Microbial Technology, vol. 47, no. 6, pp. 268–276, 2010.
[2]
D. Djabali, N. Belhaneche, B. Nadjemi, V. Dulong, and L. Picton, “Relationship between potato starch isolation methods and kinetic parameters of hydrolysis by free and immobilised α-amylase on alginate (from Laminaria digitata algae),” Journal of Food Composition and Analysis, vol. 22, no. 6, pp. 563–570, 2009.
[3]
D. Gangadharan, K. M. Nampoothiri, S. Sivaramakrishnan, and A. Pandey, “Immobilized bacterial α-amylase for effective hydrolysis of raw and soluble starch,” Food Research International, vol. 42, no. 4, pp. 436–442, 2009.
[4]
A. Illanes, “Immobilized biocatalysts,” in Comprehensive Biotechnology, vol. 1, pp. 25–39, Elsevier, 2nd edition, 2011.
[5]
P. M. Doran, “Heterogeneous reactions,” in Bioprocess Engineering Principles, pp. 297–332, Academic Press, 1995.
[6]
S. Gülay, Immobilization of thermophilic recombinant esterase enzyme by entrapment in coated Ca-alginate beads [M.S. thesis], The ？zmir Institute of Technology, 2007.
[7]
Z. Konsoula and M. Liakopoulou-Kyriakides, “Thermostable α-amylase production by Bacillus subtilis entrapped in calcium alginate gel capsules,” Enzyme and Microbial Technology, vol. 39, no. 4, pp. 690–696, 2006.
[8]
S. Talekar and S. Chavare, “Optimization of immobilization of α-amylase in alginate gel and its comparative biochemical studies with free α-amylase,” Recent Research in Science and Technology, vol. 4, no. 2, pp. 01–05, 2012.
[9]
L. N. Meyer, Effect of immobilization method on activity of alpha-amylase [thesis], The Ohio State University, 2007.
[10]
E. Demirkan, S. Dincbas, N. Sevinc, and F. Ertan, “Immobilization of B. amyloliquefaciensα-amylase and comparison of some of its enzymatic properties with the free form,” Romanian Biotechnological Letters, vol. 16, no. 6, pp. 6690–6701, 2011.
[11]
A. Riaz, S. A. U. Qader, A. Anwar, and S. Iqbal, “Immobilization of a thermostable A-amylase on calcium alginate beads from Bacillus subtilis KIBGE-HAR,” Australian Journal of Basic and Applied Sciences, vol. 3, no. 3, pp. 2883–2887, 2009.
[12]
G. Dey, B. Singh, and R. Banerjee, “Immobilization of α-amylase produced by Bacillus circulans GRS 313,” Brazilian Archives of Biology and Technology, vol. 46, no. 2, pp. 167–176, 2003.
[13]
S. Dincbas and E. Demirkan, “Comparison of hydrolysis abilities onto soluble and commercial raw starches of immobilized and free B. amyloliquefaciensα-amylase,” Journal of Biological & Environmental Sciences, vol. 4, no. 11, pp. 87–95, 2010.
[14]
A. Anwar, S. A. U. Qader, A. Raiz, S. Iqbal, and A. Azhar, “Calcium Alginate: a support material for immobilization of proteases from newly isolated strain of Bacillus subtilis KIBGE-HAS,” World Applied Sciences Journal, vol. 7, no. 10, pp. 1281–1286, 2009.
[15]
D. Park, S. Haam, K. Jang, I. S. Ahn, and W. S. Kim, “Immobilization of starch-converting enzymes on surface-modified carriers using single and co-immobilized systems: properties and application to starch hydrolysis,” Process Biochemistry, vol. 40, no. 1, pp. 53–61, 2005.
[16]
A. Horta, J. R. álvarez, and S. Luque, “Analysis of the transient response of a CSTR containing immobilized enzyme particles. Part I. Model development and analysis of the influence of operating conditions and process parameters,” Biochemical Engineering Journal, vol. 33, no. 1, pp. 72–87, 2007.
[17]
D. Jeison, G. Ruiz, F. Acevedo, and A. Illanes, “Simulation of the effect of intrinsic reaction kinetics and particle size on the behaviour of immobilised enzymes under internal diffusional restrictions and steady state operation,” Process Biochemistry, vol. 39, no. 3, pp. 393–399, 2003.
[18]
M. Dadvar and M. Sahimi, “Pore network model of deactivation of immobilized glucose isomerase in packed-bed reactors II: Three-dimensional simulation at the particle level,” Chemical Engineering Science, vol. 57, no. 6, pp. 939–952, 2002.
[19]
M. Dadvar, M. Sohrabi, and M. Sahimi, “Pore network model of deactivation of immobolized glucose isomerase in packed-bed reactors I: Two-dimensional simulations at the particle level,” Chemical Engineering Science, vol. 56, no. 8, pp. 2803–2819, 2001.
[20]
S. Loghambal and L. Rajendran, “Mathematical modeling in amperometric oxidase enzyme-membrane electrodes,” Journal of Membrane Science, vol. 373, no. 1-2, pp. 20–28, 2011.
[21]
A. E. Al-Muftah and I. M. Abu-Reesh, “Effects of internal mass transfer and product inhibition on a simulated immobilized enzyme-catalyzed reactor for lactose hydrolysis,” Biochemical Engineering Journal, vol. 23, no. 2, pp. 139–153, 2005.
[22]
S. Bhatia, W. S. Long, and A. H. Kamaruddin, “Enzymatic membrane reactor for the kinetic resolution of racemic ibuprofen ester: modeling and experimental studies,” Chemical Engineering Science, vol. 59, no. 22-23, pp. 5061–5068, 2004.
[23]
H. Zhang and Z. Jin, “Preparation of products rich in resistant starch from maize starch by an enzymatic method,” Carbohydrate Polymers, vol. 86, no. 4, pp. 1610–1614, 2011.
[24]
V. Varatharajan, R. Hoover, J. Li et al., “Impact of structural changes due to heat-moisture treatment at different temperatures on the susceptibility of normal and waxy potato starches towards hydrolysis by porcine pancreatic alpha amylase,” Food Research International, vol. 44, no. 9, pp. 2594–2606, 2011.
[25]
A. Mukherjee, A. K. Ghosh, and S. Sengupta, “Purification and characterization of a thiol amylase over produced by a non-cereal non-leguminous plant, Tinospora cordifolia,” Carbohydrate Research, vol. 345, no. 18, pp. 2731–2735, 2010.
[26]
R. S. S. Kumar, K. S. Vishwanath, S. A. Singh, and A. G. A. Rao, “Entrapment of α-amylase in alginate beads: single step protocol for purification and thermal stabilization,” Process Biochemistry, vol. 41, no. 11, pp. 2282–2288, 2006.
[27]
Z. Konsoula and M. Liakopoulou-Kyriakides, “Starch hydrolysis by the action of an entrapped in alginate capsules α-amylase from Bacillus subtilis,” Process Biochemistry, vol. 41, no. 2, pp. 343–349, 2006.
[28]
A. G. Marangoni, Enzyme Kinetics a Modern Approach, John Wiley & Sons, 2003.
[29]
J. M. Lee, Biochemical Engineering, Prentice-Hall, 2011.
[30]
M. Y. Arica, V. Hasirci, and N. G. Alaeddino？lu, “Covalent immobilization of α-amylase onto pHEMA microspheres: preparation and application to fixed bed reactor,” Biomaterials, vol. 16, no. 10, pp. 761–768, 1995.
[31]
P. Bernfeld, S. P. Colowick, and N. O. Kaplan, “Amylases α and β,” in Methods in Enzymology, vol. 1, pp. 149–158, Academic Press, New York, NY, USA, 1955.
P. Grunwald, K. Hansen, and W. Gunber, “The determination of effective diffusion coefficients in a polysaccharide matrix used for the immobilization of biocatalysts,” Solid State Ionics, vol. 101–103, part 2, pp. 863–867, 1997.
[34]
J. Coulson, M. J. F. Richardson, J. R. Backhurst, and J. H. Marker, Chemical Engineering, vol. 1, Butterworth-Heinemann, 6th edition, 1999.
