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Biotechnol Lett (2012) 34:11311135 DOI 10.1007/s10529-012-0886-7
ORIGINAL RESEARCH PAPER
A hydrophilic and hydrophobic organic solvent mixture enhances enzyme stability in organic media
Yoo Seong Choi Young Je Yoo
Received: 30 January 2012 / Accepted: 15 February 2012 / Published online: 24 February 2012 Springer Science+Business Media B.V. 2012
Abstract Binary mixtures of hydrophilic and hydro-phobic solvents were assessed for their ability to balance enzyme activity with the conservation of enzyme stability in organic media. Acetone, dioxane and dodecane were chosen as model organic solvents, and subtilisin Carlsberg and horseradish peroxidase (HRP) were chosen as model enzymes. Residual enzyme activities were measured to monitor enzyme stability, and the uorescence intensity of HRP was monitored to investigate structural changes due to the presence of an organic solvent. Enzyme stability increased with the increasing hydrophobicity of the solvent mixture used, and a solvent mixture with a high log P value (*[4) was capable of conserving enzyme stability. Enzyme stability in organic media can be conserved therefore with a mixture of hydrophilic and hydrophobic solvents: this approach might be used as a general and practical strategy for optimizing enzyme activity and stability for industrial applications.
Keywords Enzyme stability Horseradish
peroxidase Organic solvents Protease Subtilisin
Introduction
The development of enzymatic catalysis in organic solvents offers many possibilities for reactions that are not feasible in aqueous solution, including chiral synthesis and resolution, the modication of fats and oils and the production of biodegradable polymers (Krishna 2002; Hudson et al. 2005; Serdakowski and Dordick 2008). The use of enzymes in non-aqueous media affords many advantages, such as altered selectivities, pH memory, and regio-, enantio- and stereoselectivity (Krishna 2002). However, the nature of the solvent used inuences the activity and stability of enzymes to a large extent in all solvent-containing biocatalytic systems. The presence of an organic solvent always carries a risk of enzyme inactivation (Adlercreutz 1996; Serdakowski and Dordick 2008).
A variety of solvent systems have been considered for improving enzyme activity and stability, such as a monophasic aqueous-organic co-solvent system, a biphasic aqueous-organic solvent system, a nearly anhydrous organic solvent system, supercritical uids, reversed micelles and ionic liquids. In addition to solvent choice, other methods for increasing enzyme stability include the addition of antioxidants, immobilization, cross-linking, separation from deactivating reagents, variation...