Downstream processing adsorption

The same resin was used for the purification via downstream processing of carminic acid, the natural colorant extracted from cochineal. By a direct adsorption method, a crude extract was applied on the polymeric bed gel and the adsorption kinetics studied using elution with hydrochloric acid and ethanol. The desorbed pure carminic acid concentrated under vacuum yielded a final product that complied with Codex Alimentarius requirements and FAO/OMS norms. 

Figure 6.3 Nonspecific protein adsorption as a result of column degradation. White circles indicate eluted column peak heights of a new column. Black diamonds indicate eluted peak heights after the column was treated with 50 wash cycles. See text for discussion. (Data from P. Gagnon, 1997, Validated Biosystems Quarterly Resource Guide for Downstream Processing, 2(1), 1, http //www.validated.com/revalbio/library.html.)...

As with the sweetening application our most common need for CO2 removal is from natural gas prior to liquefaction. In this application we are often faced with amounts of oxygen in the feed that may range up to several hundred ppm by volume. The process is often limited to adsorption at a total pressure of about 3 5 bar. In this application however the feed gas is most often pipeline natural gas which gas will have been pre-dried to pipeline standards or about seven pounds (1 lb = 0.45 kg) of water per MMSCF of gas. In some cases the gas source may be other than pipeline and the water load needs to be estimated based on a given mole fraction. The liquefaction process, which runs at -260°F (127°C), demands very low levels of water in the product as well as trace levels of CO2 so that the heat exchangers in the downstream process remain clean. 

The growing interest in various )5-lactam antibiotics, especially the cephalosporins, over the last decade has called upon improvement in their production methods via modification of either the basic process and the microbial strain or the downstream processing techniques. The product recovery may involve various methods of extraction and purification which play an important role in the overall process economics [12]. During recent years much attention has been given to the development of liquid membrane (LM) processes which usually exhibit high extraction rates and selectivity as compared to those achievable in conventional solvent extraction and adsorption processes. 

An alternative approach is taken in the production of monosodium glutamate (MSG) which, unlike interferon, is secreted into the fermentation broth. The stages of downstream processing for MSG are shown in Figure 14.3. Again, a variety of unit operations, including centrifugation, crystallization, vaporization, and fixed-bed adsorption, are used in this process. 

In the downstream processing of bioprocesses, fixed-bed adsorbers are used extensively both for the recovery of a target and for the removal of contaminants. Moreover, their performance can be estimated from the breakthrough curve, as stated in Chapter 11. The break time tg is given by Equation 11.13, and the extent of the adsorption capacity of the fixed bed utilized at the break point and loss of adsorbate can be calculated from the break time and the adsorption equilibrium. Affinity chromatography, as weii as some ion-exchange chromatography, are operated as specific adsorption and desorption steps, and the overall performance is affected by the column capacity available at the break point and the total operation time. 

As the ligand-protein interaction takes place at the internal surface of porous adsorbents, kinetics and equilibrium of the interaction should be independent of the interstitial voidage within an adsorbent bed. Therefore the equilibrium capacity of an adsorbent will not be influenced by different experimental configurations e.g. batch stirred tank, batch fluidized bed, frontal application to packed or fluidized beds. The major difference arises from the medium from which the protein is isolated. As fluidized beds are used for whole broth adsorption, the properties of the broth have to be considered regarding the possible influence of components which are removed in conventional primary recovery steps and therefore are not present during the initial chromatography operations in a standard downstream process. These are on one hand nucleic... 

The purity of a crystalline product depends on the nature of the other species in the mother liquor from which the crystals are produced, the physical properties of the mother liquor, and the processing that occurs between crystallization and the final product (downstream processing). Impurities can find their way into the final product through a number of mechanisms the formation of occlusions, trapping of mother liquor in physical imperfections of the crystals or agglomerates, adsorption of species onto crystal surfaces, as part of chemical complexes (hydrates or solvates), or through lattice substitution. 

The most critical problem to be solved was that of unwanted HC1 adsorption ( ) on the catalyst carrier, since this resulted in the liberation of unconverted HC1 in the regeneration phase and the resulting adsorptive HC1 slip contaminated the chlorine product, thus nullifying the intended simplification of downstream processing. 

This study focuses firstly on the transfer of regeneration principles as they have been developed in the field of water-based electroplating and of purification options for ionic liquids as they are experienced in other fields of ionic liquid application. A number of purification procedures for fresh ionic liquids have already been tested on the laboratory scale with respect to their finishing in downstream processing. These include distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous chromatography. But little is known yet about efficiency on the technical scale. Another important aspect discussed is the recovery of ionic liquids from rinse or washing water. 

Low-molecular-weight products, generally secondary metabolites such as alcohols, carboxylic and amino acids, antibiotics, and vitamins, can be recovered using many of the standard operations such as liquid-liquid extraction, adsorption and ion-exchange, described elsewhere in this handbook. Proteins require special attention, however, as they are sufficiendy more complex, their function depending on the integrity of a delicate three-dimensional tertiary structure that can be disrupted if the protein is not handled correcdy. For this reason, this section focuses primarily on protein separations. Cell separations, as a necessary part of die downstream processing sequence, are also covered. 

The remainder of this introductory chapter focuses on downstream processing and bioseparation relevant to the chapters presented in this book. Thus, the following topics are covered multiphase systems, membrane separation, centrifugation and adsorption techniques, electrophoresis, chromatography, and affinity separations. 

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