Tolerance of the enzymes to organic solvents

The 3-pyridinecarboxyaldehyde 58 is highly water soluble, and so the spontaneous cyanide addition to give racemic cyanohydrin cannot be suppressed unless the aqueous pH is lowered below 3.5, which is not tolerated by the enzymes. The only available option is to operate in a 100% organic solvent system. This was recently made possible by the availability of the cross linked enzyme aggregate particles (CLEAs), which can tolerate organic solvents [64]. The individual precipitated protein molecules are chemically bonded to one another through the formation... 

The definition of a more efficient enzymatic system could be based on the separation of the catalytic cycle of the enzyme and the degradation step by the Mn3+ reactive species in MnP systems. The Mn3+-chelates present several advantages in their use as oxidants. They are more tolerant to protein denaturing conditions such as extremes of temperature, pH, oxidants, organic solvents, detergents, and proteases, and they are smaller than proteins therefore, they can penetrate microporous barriers inaccessible to proteins. The optimization of the production of the Mn3+-chelate will have to be compatible with the minimal consumption and deactivation of the enzyme. 

In many aldoi additions catalyzed by aldolases the solubility characteristics of both donor and acceptor (aldehyde) substrates differ substantially. Whilst the donor is fully soluble in aqueous medium and insoluble in organic solvents, the solubility of the acceptor is generally the reverse. Aqueous-organic cosolvent mixtures, like dimethylformamide/water, are normally used to overcome this problem. Hence, 10-20% v/v cosolvent concentration is usually well tolerated by the enzyme but not enough for substrate solubility (Sobolov et al. 1994 Budde and Khmelnitsky 1999). 

If enzymatic tracers are used, the actual detection reaction is frequently disturbed by influences exerted on the reactive center of the enzyme, especially those due to interactions of the antibody with polyfunctional groups, e.g., with the humic substances in natural water samples [15]. This should be taken into aceount, especially in the use of immunoassays for soil screening. In competitive immunoassays, analytes that are sparingly soluble in water can be solubilized by the addition of surfactants [16]. On the other hand, the surfactant can alter the tertiary structure of the antibody, and possibly of the enzyme involved. The use of organic solvents is being intensively studied [17]. In some cases, immunoassays are known to tolerate more than 10 vol % of solvent. 

The stability and activity of lipases can be improved by the pretreatment of an enzyme prior to its application. The pretreatment strategy involves exposure of an enzyme to substrate and its analogs, organic solvents, and salts. These pretreatments enhance catalytic performance by keeping the active sites in open conformation. Methanol inactivation and high price are major drawbacks for lipases in their successful use for biodiesel production. Pretreatments improve the catalytic performance, methanol tolerance, as well as stability of lipases (Guldhe et al., 2015). 

Alcohol dehydrogenase-catalyzed reduction of ketones is a convenient method for the production of chiral alcohols. HLAD, the most thoroughly studied enzyme, has a broad substrate specificity and accommodates a variety of substrates (Table 11). It efficiendy reduces all simple four- to nine-membered cycHc ketones and also symmetrical and racemic cis- and trans-decalindiones (167). Asymmetric reduction of aUphatic acycHc ketones (C-4—C-10) (103,104) can be efficiendy achieved by alcohol dehydrogenase isolated from Thermoanaerohium hrockii (TBADH) (168). The enzyme is remarkably stable at temperatures up to 85°C and exhibits high tolerance toward organic solvents. Alcohol dehydrogenases from horse Hver and T. hrockii... 

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