Isopropanol recycling system

Formate dehydrogenase in conjunction with polyethyleneglycol-immobilized nicotinamide adenine dinudeotide has been used to good effect as a cofactor recycle system (39). The alcohol dehydrogenase from Thermoanaerobium hrockii catalyzed the reduction of ketones independently when driven by the cooxidation of isopropanol (40,41). 

Ultrapure Isopropanol Purification and Recycling System (Example... 

Chary MV, KeerthysriNC,VupallapatiSVN,LigaiahN,KantevariS(2008)Tetrabutylammomum bromide (TBAB) in isopropanol an efficient, novel, neutial tmd recyclable catalytic system for the synthesis of 2,4,5-trisubstituted imidazoles. Catal Commun 9 2013-2017... 

AOD has been coimmobilized with alcohol dehydrogenase in order to increase the sensitivity of alcohol determination (Hopkins, 1985). In the presence of oxygen and NADH ethanol is recycled between the two enzymes. Thus more H2O2 is formed than substrate is present in the enzyme membrane, i.e., the sensitivity is enhanced (see also Section 3.2.4). A further advantage of this system is that this recycling is restricted to ethanol, because methanol is converted only by AOD but notbyADH. Conversely, isopropanol is oxidized by ADH but not by AOD. Thus, by combination of the two enzymes the selectivity of the sensor for ethanol is improved. 

In a few cases, this does not present a problem. DMF forms low-boiling azeotropes with heptane and xylenes. The addition of water in the fractionation system as an entrainer allows the formation of azeotropes with these hydrocarbons, but not with DMF. The hydrocarbon/water azeotrope at the column top splits into two liquid phases, so that the hydrocarbon can be removed and the water recycled. Similarly, in drying ethanol and isopropanol the unwanted water forms a separate phase which can be removed while the entrainer is recycled to pick up more water. 

The azeotropic composition of a binary system is not only influenced by recycled third components added to the mixture and by the operating pressure, but also by the presence of an insoluble inert gas, which is favorable for the separation if the volatile components of the mixture diffuse at different velocities across the regions of inert gases. Figure 2-31 a shows an example using the binary isopropanol/water mixture. Steam diffuses faster across an air bolster than isopropanol vapor, and thus, the distillate of isopropanol mole fraction is more water-rich due to the presence of air between the liquid and the condensation surfaces (point A2), compared with the distillation under air exclusion (point A,). 

ADH from Lactobacillus brevis (IBADH) was used for the synthesis of a statin side chain, used as an alternative key intermediate in the synthesis of atorvastatin (Figure 13.2). In this variant, the NADPH-dependent enzyme was highly regio-and stereoselective, reducing fert-butyl 6-chloro-3,5-dioxohexanoate to tert-butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate in 72% yield and with >99.5% ee. The cofactor was recycled in a coupled-substrate approach [1], where isopropanol was concomitantly oxidized to acetone at the expense of NADP, thereby driving the reaction toward product formation. Crude cell extract of recombinant LBADH expressed in E. coli was used in a fed-batch system on 8 1 scale, and a TTN of 2x10 could be calculated for IBADH [13-15]. 

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