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Chain length selectivity during the polycondensation of siloxane-containing esters and alcohols by immobilized Candida antarctica lipase B

Paper ID Volume ID Publish Year Pages File Format Full-Text
17210 42651 2014 6 PDF Available
Title
Chain length selectivity during the polycondensation of siloxane-containing esters and alcohols by immobilized Candida antarctica lipase B
Abstract

•We have examined the chain length selectivity for a series of acyl donors by lipase B from Candida antarctica.•Substrates studied include a series of vinyl siloxane esters and alcohols.•A Z arrangement around the double bond stalled esterification completely.•Geometry appears to play a significant role in the CalB biocatalytic system.

We have examined the chain length selectivity for a series of acyl donors by lipase B from Candida antarctica (CalB). CalB accepted aliphatic diesters of C4, C6 and C12 chain lengths equally. The introduction of a carbon–carbon double bond into the C4 esters dramatically lowered the rate constant associated with polymerization highlighting the role of geometry in catalysis; fumarate esters were polymerized at a reduced rate compared to the succinate esters, while the maleate esters were not polymerized above 5% over the course of 24 h. A disiloxane-containing diester impeded catalysis by CalB. We examined a series of vinyl siloxane esters and alcohols, and learned that the Z arrangement around the double bond stalled esterification by CalB completely. The distance between the ester carbonyl and the dimethylsiloxy group was shown to be an important factor in mediating catalysis. The rate constants were similar when the methylene spacer was 3, 4, or 5 units in length; beyond 6 methylene units, the rate constants increased. This has been tentatively attributed to the local reduction on the steric bulk when the larger siloxane moiety lies outside of the active site of the enzyme.

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Keywords
Silicon biotechnology; Lipase; Substrate tolerance; Silicon chemistry; Siloxane-polyesters
First Page Preview
Chain length selectivity during the polycondensation of siloxane-containing esters and alcohols by immobilized Candida antarctica lipase B
Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volumes 58–59, 10 May 2014, Pages 87–92
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering