Eutectic suspensions

The influence of eutectic media on the kinetics and productivity of biocatalysts has yet to be fully elucidated. Syntheses in eutectic suspensions have been scaled up to the pilot scale in a rotating drum reactor. The bioactive peptide Na-Cbz-L-Lys(Ne-Cbz)-Gly-L-Asp(OAll)-L-Glu(OAll)OEt was synthesized via a sequential N-to-C strategy in a heterogeneous solid-liquid mixture of the substrates in the presence of chymopapain and subtilisin as well as 16-20% (w/w) water and ethanol (Gill, 2002). At substrate concentrations of around 1 m, yields of 67-74% per step at product concentrations of 0.36, 0.49, and 0.48 kg kg-1 were achieved. The corresponding space-time yields were between 0.30 and 0.64 kg (kg d)-1 and biocatalyst reuse provided productivities of 166-312 kg product (kg enzyme)-1. 

As with the type II metal-based liquids (e.g. Cr) particulate suspensions are stabilized by the relatively high viscocity. A dispersion of 3 wt.% AI2O3 was made in type III eutectics and mild agitation was suffident to retain the alumina as... 

Much less work has been reported for the 6-valent elements as compared with the volume of literature for the actinides in lower valence states. Hydrated neptunium and plutonium trioxides are now known, Np03 H2O and PUO3 (0.8)H2O being readily obtained by the action of ozone on an aqueous suspension of neptunium (V) or plutonium (IV) hydroxides at 90°C. (23) Np03 2H2O is obtained in a similar manner at 18°C. (23) or by ozone oxidation of neptunium (V) in a molten lithium-potassium nitrate eutectic at 150°C. (42). 

Chiou and Riegelman classified solid dispersions intothe following six representative types 1) simple eutectic mixtures 2) solid solutions 3) glass solutions and glass suspensions 4) amorphous precipitations in a crystalline carrier 5) compound or complex formation and 6) combinations of the previous five types. 

It has been reported that in a lithium-potassium nitrate eutectic, Mn " is stabilized as a blue suspension in solutions containing OH, ... 

The possibility of overcoming encrustation problems by applying direct contact cooling techniques (section 8.4.1) has been explored for the separation of organic eutectic systems by suspension melt erystallization (Kim and Mers-mann, 1997 Bartosch and Mersmann, 1999). These laboratory studies, whieh utilized both gas (air) and liquid (water) as eoolants were aimed at measuring heat transfer and kinetic data and observing the erystal produet eharaeteristies. Eventual industrial application (section 8.2.3) appears possible. 

Figure 4. The relationship between temperature, water content, and stability (after Franks, F.f In a dilute aqueous suspension, a biochemically active molecule is structural stabile but is vulnerable to a wide range of environmental degradative forces such as hydrolysis, oxidation and racemization. In a surface immobilized or dehydrated state, a biochemically active molecule achieves peater kinetic stability at a cost of thermodynamic instability. From a dilute state (A) through supersaturation (S) with progressive water loss on the way to a solid glassy state (B), a biochemcially active molecule passes through a thermodynamically defined (entropic loss of water and enthalpy of adsorption) transition zone (stippled) where irreversible conformational changes may occur. We have observed that the disaccharides used to fabricate Aquasomes appear to stabilize biochemically active molecules in this zone during surface-induced dehydration. The dashed line represent the freeze-drying pathway between the eutectic point and Tg.

TFE and VDF can be polymerized in any proportion, thus giving rise to a broad variety of products. The copolymers are obtained in either emulsion or suspension process. An approximate composition of TFE PVDE of 20 80 is the eutectic point in the system, with a melting point of 120 ° C. It is widely used as a technical polymer and is available under the brand names Kynar 7200 and Kynar SL (Pennwalt Corporation). A composition with the an approximate composition of TFE PVDF 29 71) is available as Fluoroplast 42 (Russia). Both copolymers are soluble in ketones and esters but are insoluble in alcohols and chlorinated hydrocarbons and are mainly processed via melt extrusion at temperatures between 190 and 260 °C [27, 28]. The low-wave-number FTIR spectrum of the copolymer is depicted in Figure 3.13. 

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