Biotransformation of cephalosporin C to 7-aminocephalosporanic acid with coimmobilized biocatalyst in a batch bioreactor

Biotransformation of cephalosporin C (CPS-C) to 7-aminocephalosporanic acid (7-ACA) was carried out with coimmobilized permeabilized cells of Trigonopsis variabilis and Pseudomonas species entrapped in Ca-pectate gel beads. Good aeration and stirring during the process was assured. The analysis of this complicated biochemical process in a heterogeneous system was based on the identification of individual effects (internal diffusion, reaction) running simultaneously. A spectrophotometric method was proposed for the determination of 7-(-ketoadipyl amido) cephalosporanic acid (CO-GL-7-ACA) and 7-ACA. The reaction-diffusion model containing dimensionless partial differential equations was solved by using the orthogonal collocation method. A good agreement between experimental values and values predicted by the mathematical model was obtained. Numerical simulations were performed on the basis of following the two assumptions:- several times higher activity of both cells,- hydrogen peroxide was continuously supplied in the bioreactor.List of Symbols A m² surface of the bead - c_imol/dm³ concentration of component in the bead and/or in the solution - c_i0mol/dm³ initial concentration of component in the solution - c_l0mol/dm³ initial concentration of CPS-C in the solution - C_jl orthogonal collocation weights of the first derivation - D_eim²/s effective diffusion coefficient of the components - D_jl orthogonal collocation weights of the second derivation - k₅ dm³/(mol · s) kinetic parameter of non-enzyme reaction - K_inhmol/dm³ inhibition parameter for the first enzyme reaction - K_i dimensionless Michaelis constant for the first and second enzyme reaction, defined in Eq. (7) - K_l dimensionless inhibition parameter for the first enzyme reaction, defined in Eq. (7) - K_mimol/dm³ Michaelis constant for the first and second enzyme reaction - n number of beads - P(_i) symbol of dimensionless reaction rate, defined in Eq. (13) - r m radial coordinate inside the bead - R m radius of the bead - R(c_i) mol/(dm³ · s) symbol for reaction rate, defined in Eq. (6) - t s time - V_max mol/(dm³ · s) max. reaction rate for the first and second enzyme reaction - V_Ldm³ volume of solution excluding the space occupied by beads - voidage in batch bioreactor - _P porosity of the bead - i dimensionless effective diffusion coefficient of the components, defined in Eq. (7) - dimensionless time, defined in Eq. (7) - _mi Thiele modulus, defined in Eq. (7) - _i dimensionless concentration, defined in Eq. (7) - dimensionless radial position inside the bead, defined in Eq. (7) - _l0 initial dimension concentration of CPS-C, defined in Eq. (9), (10) - _i0 initial dimension concentration of component, defined in Eq. (9), (10)The authors wish to thank Dr. P. Gemeiner of Slovak Academy of Sciences for rendering of pectate gel. This work is supported by Ministry of Education (Grant No. 1/990 935/93).