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Catalysts 2017, 7(8), 227; doi:10.3390/catal7080227

Effect of Water Clustering on the Activity of Candida antarctica Lipase B in Organic Medium

1
Department of Chemistry, Technical University of Denmark, Building 207, 2800 Kgs, Lyngby, Denmark
2
Department of Chemical and Biochemical Engineering, Technical University of Denmark, Building 229, 2800 Kgs, Lyngby, Denmark
*
Authors to whom correspondence should be addressed.
Received: 10 July 2017 / Revised: 21 July 2017 / Accepted: 25 July 2017 / Published: 29 July 2017
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Abstract

The effect of initial water activity of MTBE (methyl tert-butyl ether) medium on CALB (Candida antarctica lipase B) catalyzed esterification reaction is investigated using experimental methods and classical molecular dynamics (MD) simulations. The experimental kinetic studies show that the initial reaction rate of CALB-catalyzed esterification reaction between butyric acid and ethanol decreases with increasing initial water activity of the medium. The highest rate of esterification is observed at the lowest water activity studied. MD simulations were performed to gain a molecular insight on the effect of initial water activity on the rate of CALB-catalyzed reaction. Our results show that hydration has an insignificant effect on the structure and flexibility of CALB. Rather, it appears that water molecules bind to certain regions (“hot spots”) on the CALB surface and form clusters. The size of the water clusters at these hot spot regions gradually increase and expand with increasing water activity. Consequently, the surface area of CALB covered by the water molecules also increases. Specifically, our results indicate that a particular water cluster located close to the active site partially cover the binding pocket of substrate at high water activity. As a consequence, the effective concentration of substrate at the catalytic site decreases. Therefore, the reaction rate slows down with increasing water activity, which correlates well with the observed decrease in the experimentally determined initial reaction rate. View Full-Text
Keywords: Candida antarctica Lipase B; Computational Study; Kinetics Study; Water activity Candida antarctica Lipase B; Computational Study; Kinetics Study; Water activity
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Dutta Banik, S.; Nordblad, M.; Woodley, J.M.; Peters, G.H. Effect of Water Clustering on the Activity of Candida antarctica Lipase B in Organic Medium. Catalysts 2017, 7, 227.

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