The process of thermodialysis and the efficiency increase of bioreactors operating under non-isothermal conditions

When a catalytic membrane is employed in a non-isothermal bioreactor its ac tivity increases as a direct function of the applied temperature gradient a nd decreases when both average temperature or substrate concentration incre ase. To know the physical cause responsible for this behaviour substrate fl uxes have been studied under isothermal conditions (diffusion) and non-isot hermal conditions (thermodialysis). Strong analogies between the behaviour of the catalytic membrane and the substrate fluxes produced by the process of thermodialysis have been observed. By introducing diffusive and thermodi ffusive substrate fluxes in appropriate mass balance equations the substrat e concentration profiles into the catalytic membrane have been deduced by c omputer simulation. In absence of catalysis and under non-isothermal condit ions the profiles are higher than the ones corresponding under comparable i sothermal conditions, while the contrary occurs in the presence of catalysi s. The percentage increases of enzyme activity, calculated by the curves of the substrate concentration profiles, show the same temperature and concen tration dependence than those actually observed with the catalytic membrane . The role of thermodialysis in affecting the enzyme activity in non-isothe rmal bioreactor has been discussed and demonstrated. (C) 2000 Elsevier Scie nce B.V. All rights reserved.