Autor(es):
Ribeiro, Adriano S. 
; Ferreira, Olga ; Macedo, Maria E. ; Loureiro, José M.
Data: 2005
Identificador Persistente: http://hdl.handle.net/10198/2174
Origem: Biblioteca Digital do IPB
Assunto(s): Biocatalysts; Mass-transfer limitations; Effectiveness factor
Descrição
Immobilized enzymes are being increasingly used as biocatalysts in numerous processes to obtain high-value products for the pharmaceutical, flavour and fragrance industries (Gandhi et al., 2000). The
major advantages of immobilization include the increase in enzyme stability, the possibility of enzyme reutilization and the easy separation of the biocatalysts from the reaction mixture. However, it is
necessary to account for mass transfer limitations that, under some conditions, may arise in these systems (Gómez et al., 2003; Jeison et al., 2003). These resistances comprise the effects of intraparticle diffusion and external mass-transfer. Given the complexity of the kinetics of multisubstrate enzyme reactions, reactor modelling studies that account for mass-transfer phenomena are so far limited to single-substrate ones (Gómez et al., 2003).
To compare the observed reaction rate with the reaction rate in the absence of mass-transfer limitations, an overall effectiveness factor is usually calculated (Gómez et al., 2003; Jeison et al., 2003). In this work, a model is developed to calculate the overall effectiveness factor for immobilized enzymes that carry out irreversible two substrates-two products reactions following kinetic mechanisms such as the Ternary Complex or the Ping-Pong Bi-Bi with inhibition by the second
substrate.
The model has two dimensionless parameters for each substrate – Thiele modulus
(reaction/intraparticle diffusion), Biot number (film diffusion/intraparticle diffusion) – and one related to the reaction kinetics. Their influence on the effectiveness factor is analysed. The
results obtained can be applied in the design and simulation of enzymatic reactors.
