Derivatized celluloses

As mentioned previously, cellulosic phases as well as amylosic phases have also been used extensively for enantiomeric separations more recently (89,90). Most of the work ia this area has been with various derivatives of the native carbohydrate. The enantioresolving abiUties of the derivatized cellulosic and amylosic phases are reported to be very dependent on the types of substituents on the aromatic moieties that are appended onto the native carbohydrate (91). Table 3 fists some of the cellulosic and amylosic derivatives that have been used. These columns are available through Chiral Technologies, Inc. and J. T. Baker, Inc. 

Bose, A. Aqueous Size Exclusion Chromatography of Non-Derivatized Cellulose Application of Excluded Volume Concepts to Calibration Ph.D. Thesis, Purdue Univ., LaFayette, IN, 1980. 

H. Ding, N. Grinberg, R. Thompson, and D. Ellison, Enantiorecognition mechanisms for derivatized cellulose under reversed phase conditions, J. Liq. Chrom. Relat. Technol. 23 (2000), 2641-2651. 

In another study, thermodynamic parameters have been investigated with a tris(4-methyIbenzoate)-derivatized cellulose type CSP (Chiralcel OJ) and a chiral diol compound. It was found that at low temperatures, the enantioselectivity is entropy-driven (region 11), while at higher temperatures the separation is enthalpy-driven (region 1) (see Fig. 9.8). DSC and IR experiments revealed that the transitions between the enthalpic and the entropic regions of the van t Hoff plots are a result of a change in conformation of the stationary phase [76]. 

Feuerstein I, Rainer M, Bernai do K, Stecher G, Huck CW, Kofler K, Pelzer A, Hominger W, Klocker H, Baitsch G, Bonn GK (2005) Derivatized cellulose combined witli MALDI-TOF MS A new tool for serum protein profiling. J Proteome Res 4 2320—2326. 

Manganaro IF and Goldberg BS. Protein pruification with novel porous sheets containing derivatized cellulose. Biotechnol. Prog. 1993 9 285-290. 

Microcrystalline cellulose II, like the cellulose I form, does not possess enough mechanical strength to be used as an HPLC-CSP Although its triacetate derivative, CTA-II, can be used as an HPLC support, it is not as useful a CSP as CTA-I (47). Ichida et al. (48) were able to improve on the properties of derivatized cellulose II by depolymerization, followed by coating on macroporous silica gel. In this manner, they created a number of new CSPs, the cellulosic CSPs, based on ester and carbamate derivatives of cellulose (see Table 2). 

Ion-exchange supports based on derivatized cellulose and agarose have been popular since the 1960s, particularly for protein analysis. For high-performance liquid chromatography (HPLC), less compressible supports, such as silica and cross-Unked polymers, are most commonly used. 

Michaels JD, Kunas KT Papoutsakis ET (1992) Fluid-mechanical damage of freely-suspended cells in agitated bioreactors effects of dextran, derivatized celluloses and polyvinyl alcohol. Chemical Engineering Communications 118 341-360. 

Michaels et al. (1992) have recently reported the beneficial effect of methocel (MW 15 000, 50 000 and 100 000) on CHO cells in agitated and aerated bioreactors. This is the only recent and complete (with control experiments) reported study of derivatized celluloses as shear protectants in bioreactors. These findings appear very promising, but additional work will be needed before the widespread use of MCs as shear protectants. 

A number of methods are being tested for enzyme immobilization. The method selected depends on the operating details of the enzyme system employed and the nature of the solvent to be used, which is usually water. Enzyme, or inactivated cells, may be encapsulated in a film, or encased in a gel, which is permeable to both the substrate and product, but not to enzyme [77]. Porous glasses or insoluble polymers such as a derivatized cellulose may be used as a support onto which enzyme is adsorbed. Pendant functional groups of a polymer, such as those of the ion-exchange resins, can be used either to ionically bind the enzyme to the resin active sites or to covalently bond the enzyme to the resin [79]. The enzyme may be bonded to a polymer backbone chain using a bifunctional monomer such as glutaraldehyde to react with enzyme sites that do not affect its catalytic activity [80]. 

Immobilization is the process of adhering biocatalysts (isolated enzymes or whole cells) to a solid support. The solid support can be an organic or inorganic material, such as derivatized cellulose or glass, ceramics, metallic oxides, and a membrane. Immobilized biocatalysts offer several potential advantages over soluble biocatalysts, such as easier separation of the biocatalysts from the products, higher stability of the biocatalyst, and more flexible reactor configurations. In addition, there is no need for continuous replacement of the biocatalysts. As a result, immobilized biocatalysts are now employed in many biocatalytic processes. 

The nylon-based membranes have several advantages over the derivatized cellulose membranes. They are thin, much more durable and have a much higher capacity (up to about 0.5 mg/cm Gershoni and Palade, 1982), probably due to its numerous positive charges. These membranes are particularly efficient with SDS-proteins. A disadvantage of nylon-based membranes is that anionic dyes cannot... 

Other important secondary products of cellulose are esters and ethers. Esters can be used for fibers and films, but also for varnishes and molding materials. The most important representative of ether derivatives is carboxymethylcellulose, which has widespread applications as a thickener, binder, and graying inhibitor in detergents. Despite the versatile possibilities to derivatize cellulose, only 0.5% of worldwide felling is used for chemical refining. Detailed information about the fundamentals and functionalization of cellulose can be found in [12, 13]. 

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