| Expanded bed adsorption (EBA) is a novel bioseparation technique, which integrates clarification, concentration and initial purification into a single unit operation. It enables proteins to be recovered directly from unclarified cultivations of microorganisms or cells and homogenates of disrupted cells, without the need for prior removal of suspended solids. Matrix is the principal "hardware" pillar supporting the successful application of EBA. The basic criteria of the matrices for EBA are formulated as being a sufficiently high density and an appropriate size distribution.The purpose of this work is to develop a spherical TiO2-densified cellulose composite matrix for EBA, through the method of water-in-oil suspension thermal regeneration. After activated by epichlorohydrin and coupling with diethylamine, the matrix was derived to function as an anion exchanger (Cell-Ti DEAHP). The matrix was also crosslinked by epichlorohydrin and attached to monochloroacetic acid to produce a cation exchanger (Cell-Ti CM). The expansion behavior, hydrodynamic properties and protein adsorption capacities of two adsorbents were investigated. Finally, the anion exchanger was used to recover dehalogenase from unclarified cell homogenate, while the cation exchanger was introduced to purify nattokinase directly from fermentation broth.The thesis is divided into four sections. The focus of Section 1 is the review of advances in matrices for EBA, including physicochemical properties required, matrices in use as well as their preparation methods. On the base of analyzing and comparing merits and drawbacks of the available matrices for EBA, the author put forward his study idea, which adopted the composite of regenerated cellulose and superfine TiO2, respectively as reactive matrix and densifier, to prepare a spherical hydrophilic matrix for EBA. Furthermore, a series of methods for analysis and characterization of the prepared matrix or adsorbent were established.Section 2 involves the preparation of the composite matrix and its derivation to function as ion exchangers. Some factors influencing the forming of cellulose-TiO2 beads were investigated in details. The optimal preparing conditions were found to be as follows: the initial viscosity of cellulose xanthate ranging from 5,000 to 8,000 cSt, the mixture of pump oil and chlorobenzene with a 6:1 mass ratio as disperse phase, the mass ratio of disperse phase to water phase at 6:1, the mixing speed at 350 ~ 400 rpm. Under these conditions, the prepared matrix had regular sphericity and a similar size distribution to that of the commercial Streamline matrix. The study also shows that the increase of TiO2 content lead to the ascent of particle density but had few effects on the pore structure, confirming that superfine TiO2 had been successfully entrapped in the regenerated cellulose matrix. A typical matrix (Cell-Ti) with some physical properties as follows: wet density 1.21 g/cm3, specific surface area 38.7 m2/mL, porosity 83.7%, and water content 69.5%, was attained.In order to hold more epoxy groups for subsequent ionization, several factors affecting the efficiency of activation reaction, such as the amount of epichlorohydrin, the concentrationof NaOH solution, and the contents of TiO2 and cellulose in matrix, were investigated emphatically. Reacted with excessive epichlorohydrin and dipped in 2.5-3.0 M NaOH solution, the content of epoxy groups in activated Cell-Ti was found to be up to 220 μ mol/mL. This content resulted in a high anion exchange capacity of 0.2 mmol Cl-/mL. Epichlorohydrin was also used to crosslink chemically the composite matrix, showing improved mechanical intensity. After coupling with monochloroacetic acid, the matrix was functioned as a cation exchange, whose exchange capacity was found to be 0.22 mmol Na+/mL. SEM photography shows that Cell-Ti had a macroporous structure.In Section 3, the 5th chapter studies the expansion characteristics of the aimed adsorbents and their liquid mixing performance in an expanded bed, while the 6th chap...
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