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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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876 Tsuneo Yamane<br />

It has been shown that a number <strong>of</strong> enzymes suspended in anhydrous (dry) organic solvents<br />

exhibit thermal stability far superior to that in aqueous solutions (Table 14.4.3.2). 11<br />

This is because most <strong>of</strong> chemical processes that occur in the thermal inactivation involve<br />

water, and therefore do not take place in a water-free environment. Furthermore, increased<br />

rigidity in dry organic solvents hinders any unfolding process. The increased thermal stability<br />

in the dry organic solvent drops down to the stability in aqueous solution by adding small<br />

amount <strong>of</strong> water as demonstrated by Zaks and Klibanov 12 and others. Thus, thermal stability<br />

<strong>of</strong> the enzyme in organic solvent strongly depends on its free water content.<br />

Table 14.4.3.2. Stability <strong>of</strong> enzymes in non-aqueous vs. aqueous media. [Adapted, by<br />

permission, from ‘Enzymatic Reactions in organic Media’, A. M. P. Koskinen and A. M.<br />

Klibanov, Blackie Academic & Pr<strong>of</strong>essional (An Imprint <strong>of</strong> Chapman & Hall), Glasgow,<br />

1996, p. 84]<br />

PLL<br />

Candida lipase<br />

Chymotrypsin<br />

Enzyme Conditions Thermal property References<br />

tributyrin<br />

aqueous, pH 7.0<br />

tributyrin/heptanol<br />

aqueous, pH 7.0<br />

octane, 100 o C<br />

aqueous, pH 8.0, 55 o C<br />

t 1/2

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