Separation systems, biochemical

An artificial system was created to elegantly demonstrate the basic principle of the chemiosmotic hypothesis. Synthetic vesicles containing bacteriorhodopsin, a purple-membrane protein from halobacteria that pumps protons when illuminated, and mitochondrial ATP synthase purified from beef heart were created (Figure 18.26). When the vesicles were exposed to light, ATP was formed. This key experiment clearly showed that the respiratory chain and ATP synthase are biochemically separate systems, linked only by a proton-motive force. 

One of the objectives of a biochemical separation system design is to minimize the number of steps (Figure 1) One way of accomplishing this is to perform the separation and concentration in situ that is directly with the whole fermentation broth using solids phase adsorbents. This type of separation requires the design of an affinity bead that provides for selective product removal from the fermentation broth. 

Although the general principles of separation processes are applicable widely across the process industries, more specialised techniques are now being developed. Reference is made in Chapter 13 to the use of supercritical fluids, such as carbon dioxide, for the extraction of components from naturally produced materials in the food industry, and to the applications of aqueous two-phase systems of low interfacial tensions for the separation of the products from bioreactors, many of which will be degraded by the action of harsh organic solvents. In many cases, biochemical separations may involve separation processes of up to ten stages, possibly with each utilising a different technique. Very often, differences in both physical and chemical properties are utilised. Frequently... 

The first two points represent a general motivation for miniaturization in separation science independent of the actual fabrication technology. The benefit of a reduction of the consumption of sample, reagents, and mobile phase in chemical and biochemical analysis is self-evident and does not need to be discussed further (reduced consumption of precious samples and reagents, reduced amounts of waste, environmental aspects). This advantage is, however, sharply contrasted by its severe implications on the detection side, as discussed elsewhere in this volume in detail. The detection of the separated zones of very small sample volumes critically depends on the availability of highly sensitive detection methods. It is not surprising that extremely sensitive laser-induced-fluorescence (LIF) has been the mostly used detection principle for chip-based separation systems so far. 

Although the pressurized ion exchange equipment was patterned after systems being studied for biochemical separations, it was operated somewhat differently. For actinides, the speed of separation is critical because of radiation effects, and it was practical to trade off some resolution for a faster separation. 

As potential directions for the BAHLM systems development, drug separations from biochemical mixtures, fermentation, catalysis and separation with enrichment of valuable compounds (BAHLM bioreactors), desalination of wastewater, and sea water and some integrated water-soluble complexing/filtration techniques are considered. It is suggested that the proposed BAHLM techniques may successfully and effectively replace the presenting separation systems with lower capital and operational costs. 

Microchip technology (see Ref. 454 and Fig. 17) is revolutionizing chemical and biochemical testing. The microchip processes fluid rather than electrons. Both electrophoretic and electroosmotic techniques are used to pump the fluid. Pumps, valves, volume-measuring devices, and separation systems are on the microchip s surface. Microchip separation procedures include electrophoresis, chromatography and solid-phase biochemistry. Microchips allow true parallelism, miniaturization, multiplexing, and automation, and these key features provide a set of performance specifications that cannot be achieved with earlier technologies (64-68,454-463). 

In terms of the amount of literature developed, biochemical separations have been largely ignored by those in the field of LEM-mediated separations. One application that has enjoyed some experimental scrutiny is that of the use of LEMs in drug delivery and overdose prevention systems. They have been used to separate or release several different types of drugs including acetylsalicyclic acid (18), phenobarbital (19), and several barbiturates (20,21). 

LEM systems have also been shown to be successful in separating commodity-type biochemicals such as propionic acid (10) and acetic acid (10,22) and have been used for the preparation of L-amino acids from racemic D,L mixtures by means of enzymatic hydrolysis of amino acid esters (23). In addition to biochemical separations, the work of Mohan and Li showed that enzymes could be encapsulated in liquid emulsion membranes with no deleterious effect on enzyme action (24). Later work by these authors indicated that encapsulated live cells could remain viable and function in the LEM interior phase for period as long as five days (25). 

The biocompatibility, fast separation process and the ease to scale up are some of the characteristics that make aqueous two-phase systems an attractive alternative to other known techniques when biochemical separation is to be carried out. 

Acryl amide, a resin usually found in research labs, is used to make gels for biochemical separations. It can cause eye and skin irritation. Long-term exposure could result in central nervous system disorders. Consider acryl amide as a suspected carcinogen and mutagen. 

The retention and the selectivity of separation in RP and NP chromatography depend primarily on the chemistry of the stationary phase and the mobile phase, which control the polarity of the separation systems. There is no generally accepted definition of polarity, but it is agreed that it includes various selective contributions of dipole-dipole, proton-donor, proton-acceptor, tt-tt electron, or electrostatic interactions. Linear Free-Energy Relationships (LFER) widely used to charactaize chemical and biochemical processes were successfiiUy apphed in liquid chromatography to describe quantitative structure-retention relationships (QSRR) and to characterize the stmctural contributions to the retention and selectivity, using multiple linear correlation, such as Eq. 

Liang, L., Stevens, J.G., Raman, S., Farrell, J.T. The use of dynamic adaptive chemistry in combustion simulation of gasoline surrogate fuels. Combust. Flame 156, 1493-1502 (2009b) Liao, J.C., Lightfoot, E.N. Lumping analysis of biochemical reaction systems with time scale separation. Biotechnol. Bioeng. 31, 869-879 (1988)... 

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