Understanding water effect on Candida antarctica lipase B activity and enantioselectivity towards secondary alcohols
2009 (English)In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, Vol. 59, no 1-3, 90-95 p.Article in journal (Refereed) Published
The effect of water activity (a(w)) on Candida antarctica lipase B (CALB) activity and enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aw was defined. The data showed a pronounced aw effect on both activity and enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aw increased enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aw, water decreased enantioselectivity, due to an unfavourable increase of the entropic term T Delta(R-S)Delta S-double dagger of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aw allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.
Place, publisher, year, edition, pages
2009. Vol. 59, no 1-3, 90-95 p.
Lipase, Stereoselective catalysis, Thermodynamics, Thermodynamic, activity of water, Water adsorption, pseudomonas-cepacia lipase, stereospecificity pocket, gas/solid system, temperature, solvent, stereochemistry, substrate, entropy, rugosa
IdentifiersURN: urn:nbn:se:kth:diva-18432DOI: 10.1016/j.molcatb.2009.01.008ISI: 000266128100012ScopusID: 2-s2.0-64649100580OAI: oai:DiVA.org:kth-18432DiVA: diva2:336479
QC 201005252010-08-052010-08-052011-01-31Bibliographically approved