Substrate preferences for lipase‐mediated acyl‐exchange reactions with butteroil are concentration‐dependent

Abstract

Substrate preferences for pancreatic lipase~mediated acylexchange reactions with butteroil were concentrationdependent for the series of acyl donors and alcohol acceptors evaluated. For acidolysis reactions, the initial reao tion rates and percent reaction yields after 18 h at 50 pmol acyl donor per gram substrate mixture were similar for nfatty acids and their methyl and glycerol esters. At 400-500 pmol g-1 (and greater), order of initial reaction rates and percent reaction yield was fatty acid glycerol esters > fatty acid methyl esters > fatty acids. At concentrations above 300-500 ~nol g-X, reaction inhibition was observed for fatty acid substrates, and inhibition took place at lower concentrations for the shorter-chainlength fatty acids of those evaluated (5-17 carbons}. Inhibition was primarily attributed to acidification of the microaqueous environment of the lipase. Desorption of water by the fatty acid substrate may be a secondary mode of inhibition. The concentration dependence of initial reaction rates and percent reaction yield was similar for the n-alcohol substrates evaluated (2-15 carbons} for alcoholysis reactions with butteroil. Optimum alcohol concentration was 375-500 pmol g-1 (except for butanol, which was 1 mmol g-l), above which reaction inhibition was observed. Inhibition was attributed to desorption of water from the enzyme by the alcohol substrate. Relative reactivity of classes of alcohols for this reaction system was primary alcohols > secondary alcohols > tertiary alcohols. Generally, alcoholysis reactions were faster than acidolysis reactions, and triacylglycerols were the best substrates for acidolys'rs reactions with butteroil at high levels (up to 2 mmol g-l) of acyl donor substrate.

Kinetics of lipase‐catalysed interesterification of triolein and caprylic acid to produce structured lipids

“…Therefore, it seems that an excess of caprylic acid above a molar ratio of approximately 6, diminishes the reaction rate. This observation concurs with the data of Kuo and Parkin, 24 and is explained by the acidification of the enzyme layer caused by an excess of the free fatty acids. 24 However, since the hydrolysis of triglycerides to diglycerides should precede the exchange of fatty acid, this decrease may also be provoked by the decrease of intermediate diglycerides that give rise to an increase in the free fatty acid concentration.…”

“…This observation concurs with the data of Kuo and Parkin, 24 and is explained by the acidification of the enzyme layer caused by an excess of the free fatty acids. 24 However, since the hydrolysis of triglycerides to diglycerides should precede the exchange of fatty acid, this decrease may also be provoked by the decrease of intermediate diglycerides that give rise to an increase in the free fatty acid concentration. This result is consistent with the results of Akoh and Huang, 11 who, working with the same system, found that the maximum proportion of dicapryl, oleilglycerol (C37 in their nomenclature) was obtained with a molar ratio range of 4-6.…”

Enzymatic modification of triolein: Incorporation of caproic and butyric acids to produce reduced‐calorie structured lipids

“…This could also be true with the increase of caproic and butyric acid in our reaction medium. This increase was attributed to acidification of the microaqueous environment of the lipase (16).…”

Synthesis of cocoa butter triacylglycerols using a model acidolysis system

“…This result is consistent with the findings of (Yankah and Akoh 2005), and Paez et al (2003). Excess free fatty acids in the medium acidify the enzyme layer because of high levels of free or ionized carboxylic acid groups or cause desorption of water from the interface which causes a decrease in the activity of the enzyme (Kuo and Parkin, 1993). In addition, high substrate ratios are economically unfeasible, because purification of the products would require a cost-increasing extra separation step.…”