Reduction solvent engineering

The use of water-miscible organic solvent-water mixtures is a particularly attractive method for use with cofactor-dependent enzymes due to its simphcity. The high water content can allow dissolution of both enzyme and cofactor, whilst the water-miscible solvent can provide a dual role in both substrate dissolution and as a cosubstrate for cofactor recycling (substrate-coupled cofactor recycling).The asymmetric reduction of a ketone intermediate of montelukast using an engineered ADH in the presence of 50 % v/v isopropanol offers a powerful demonstration of this methodology (Scheme 1.55). 

Reaction engineering helps in characterization and application of chemical and biological catalysts. Both types of catalyst can be retained in membrane reactors, resulting in a significant reduction of the product-specific catalyst consumption. The application of membrane reactors allows the use of non-immobilized biocatalysts with high volumetric productivities. Biocatalysts can also be immobilized in the aqueous phase of an aqueous-organic two-phase system. Here the choice of the enzyme-solvent combination and the process parameters are crucial for a successful application. 

This chapter shows how a biphasic medium can help in reducing loss of volatile compounds in a gaseous phase exiting from a bioreactor, in comparison with pure aqueous systems. It also emphasises the usefulness of solvents having low vapour pressure (heavy organic solvents or ionic liquids) in the reduction of the release of compounds into the environment. There are, from this point of view, common interests between engineering needs and environmental concerns in the flavouring industry. 

As provider of Chemical Leasing services PERO Innovative Services was able to include in the project all peripheral devices necessary for the supply, reconditioning, recovery and maintenance of the chemicals. The equipment was engineered based on the principle of cost reduction with regard to chemicals consumption, energy consumption, supply of spare parts and service. The solvent and the stabilisers used were adapted to the specific cleaning needs of Automobiltechnik Blau. 

Figure 3.5 displays the total wastes produced by the pharmaceutical industry and shows results similar to those in Figure 3.4. Figure 3.5 includes the on-site and off-site disposal, treatment, and release of toxic and hazardous materials. With the implementahon of green engineering and chemistry practices, there have been many improvements in the areas of process development and solvent selection. These innovations have led to solvent and energy reductions in many processes used today and the subsequent reduction of process waste disposal. Between 1995 and 2006, there was an approximate 47.6 million kilogram decrease in the total yearly amount of waste disposed of from the pharmaceutical sectors. 

Bidirectional PCET is also featured on the reduction side of the photosynthetic apparatus. In the bacterial photosynthetic reaction center, two sequential photo-induced ET reactions from the P680 excited state to a quinone molecule (Qg) are coupled to the uptake of two protons to form the hydroquinone [213-215]. This diffuses into the inter-membrane quinone pool and is re-oxidized at the Qq binding site of the cytochrome bcj and coupled to translocation of the protons across the membrane, thereby driving ATP production. These PCET reactions are best described by a Type D mechanism because the PCET of Qg appears to involve specifically engineered PT coordinates among amino acid residues [215]. In this case PT ultimately takes place to and from the bulk solvent. Coupling remains tight in... 

Very extensive laboratory work on all phases of the use of catalytic reduction to produce both aliphatic and aromatic amines has been reported in the literature. Studies have been carried out on many types of catalysts, catalyst supports, promoters and poisons, solvents, temperatures, pressures, and equipment. Considerable pilot-plant work and engineering studies have been undertaken and a number of commercial installations built for batch catalytic reduction and for continuous catalytic reduction. Commercial installations are now in operation for the catalytic reduction of nitro compounds and nitriles. 

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