Internal and external mass transfer limitations on the activity of immobilised acid urease derivatives differing in enzyme loading

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• 作者：Nadia Bortone ; Marcello Fidaleo ; Mauro Moresi
• 关键词：Diffusion-reaction model ; Effectiveness factor ; Enzyme loading ; Eupergit® ; C 250 L supports ; Immobilised acid urease ; Liquid mass transfer coefficient ; Model wine solution ; Urea degradation kinetics
• 刊名：Biochemical Engineering Journal
• 出版年：15 January, 2014
• 年：2014
• 卷：82
• 期：Complete
• 页码：22-33
• 全文大小：816 K

文摘

The specific activity of several Eupergit庐 C 250 L immobilised acid urease derivatives with enzyme loadings (Y_P/B) of 48-171 mg of bovine serum albumin equivalent (BSAE) per gram of dry support (ds) in a model wine solution was satisfactorily reconstructed using the simultaneous film and intraparticle diffusion and Michaelis-Menten kinetic model by assuming that the immobilisation procedure did not alter the intrinsic kinetic parameters of free acid urease. The behaviour of crunched biocatalysts resulted to be practically coincident with that of the free enzyme, while that of the whole beads was affected by diffusional effects. The model prediction capability was also established in long-time reaction tests using two other biocatalysts at different dry bead concentrations (c_Bd). The effect of Y_P/B was finally simulated in the pseudo-1st order regime in the presence of a stagnant or highly-stirred medium. At the limiting Sherwood number of 2.0 and Y_P/B > 48 mg BSAE g^鈭? ds, the calculated specific activity was greatly affected by external mass transfer. To help designing stirred bioreactors, the substrate reduction to be achieved in a given time interval was empirically related to c_Bd and Y_P/B.