Md. M. Hossain

Step elution in preparative liquid chromatography

Preparative liquid chromatography with the step elution, in which a sample is loaded into a column at higher binding strength and then eluted at lower binding strength, was numerically simulated with a detailed rate equation model. The model takes into account film mass transfer resistance, pore diffusion, axial dispersion and local equilibrium. The step elution mode was compared with the isocratic elution mode in terms of the preparative performance for a binary mixture having a constant or variable separation factor. The effects of various parameters, such as step height, sample size, solute concentration, feed composition and mobile phase flow-rate, were examined.

The effects of denaturation in the displacement chromatographic behaviour of proteins

The denaturation of proteins is characterized by an equilibrium between a native and a partially denatured protein, which is then irreversibly denatured to an inactive form. A comprehensive rate equation model has been developed for multicomponent displacement chromatography incorporating: (i) denaturation kinetics; (ii) intraparticle diffusion; (iii) film mass transfer transfer; (iv) finite adsorption rate; (v) axial dispersion in the mobile phase. The effects of equilibrium constant, rate constant of denaturation, particle size, velocity and column length were investigated. The simulation results show that the denaturation reaction influences the shape of the chromatograms considerably, especially in cases where fast equilibration between native and partially denatured proteins occurs and where the rate constant of denaturation is very high. The chromatograms also suggest the use of smaller particle size, slow velocity and shorter column length for higher productivity of desired proteins and lower concentration of inactive protein.

Immobilization of multi-enzyme in porous solid supports—a theoretical study

A theoretical study is presented dealing with the immobilization of two enzymes into a porous solid support. The developed model basically takes into account the interplay between restricted diffusions of two enzymes within intraparticle void space and their competitive adsorptions onto available functional sites on the interior surfaces. Simulations have shown that parameters such as binding rates of enzymes, initial bulk concentration ratio, pellet size and impregnating time have significant influence on the eventual distribution of two enzymes within the porous solid supports.

Effects of nonuniform immobilized enzyme distribution in porous solid supports on the performance of a continuous reactor

Abstract A comprehensive model for an immobilized enzyme reactor is developed to study the performance of a nonuniform biocatalyst in a continuous stirred basket reactor. Numerical simulations have been carried out to study the influence of particle size on enzyme stability and effectiveness. The advantages of nonuniform profiles have been shown for moderate to large values of the Thiele modulus for systems obeying Michaelis-Menten kinetics. Experimental results [1] for hydrogen peroxide-immobilized enzyme on controlled-pore glass and SiAl particles were re-analyzed using the information obtained for the nonuniform distribution of immobilized enzyme. It is demonstrated that the deactivation data obtained in a continuous stirred basket reactor are followed much more closely by the nonuniformly than by the uniformly distributed enzyme model.