Control of the regiospecificity of Candida antarctica lipase by polarity

Regiospecificity of Immobilized Candida antarctica Lipase B (CAL-B) towards 2,3-Diacyl-1-O-alkyl Glyceryl Ether in Ethanol

Highly pure 2,3-dioleoyl-1-O-alkyl glyceryl ether (DOGE), whose 1-position is a lipase-tolerant ether bond, was chemically synthesized and its detailed regioselectivity and acyl transfer were confirmed. During ethanolysis using immobilized Candida antarctica lipase B (CAL-B) with DOGE as the substrate, monooleoyl-1-O-alkyl glyceryl ethers (MOGEs) and a few 1-alkyl glyceryl ethers were formed upon consumption of the substrate. The structure of MOGE was confirmed using nuclear magnetic resonance spectroscopy and only the isomer of 2-MOGE was formed, indicating that CAL-B has complete α- regiospecificity. During ethanolysis, 3-MOGE was formed via acyl migration. These results indicate that the formation of 1-alkyl glyceryl ethers is not due to the imperfect regiospecificity of CAL-B, but rather due to ethanolysis of the formed 3-MOGE. The ethanolysis rate at the 3-α-position of DOGE was faster and the rate of acyl transfer was slightly slower for chain lengths greater than 14. These results show for the first time that both deacylation at the 3-position and acyl migration from the 2- to 3-position are affected by the structure of 1-position.

Seasonal variation in the positional distribution of fatty acids in bovine milk fat

The aim of this study was to determine the seasonal variation in the positional distribution of fatty acids (FA) in bovine milk fat. Bovine milk samples were collected from May 2017 to April 2018 in the Netherlands, and the FA composition in the sn-2 position was determined by using sn-1(3)-selective transesterification of Candida antarctica lipase B. The majority of the FA showed significant variation at sn-2 and sn-1(3) positions between different seasons. The seasonal variation in sn-2 position was higher than the sn-1(3) positions. Parallel to the changes in the diet of the cows throughout a year, we observed an increase in blood-derived FA (i.e. C18:0, C18:1 cis-9) concentrations and a decrease in de novo-synthesized FA during summer. In winter, more saturated FA were esterified in sn-2 position of milk fat. Highest concentrations of palmitic acid, C16:0, was observed in sn-2 position in winter, whereas the amount of unsaturated FA at this position was highest in summer. These results showed that the FA compositions in different regiospecific positions changed due to season; however, the proportions of a specific FA within the 3 positions of the triacylglycerols in milk fat did not change upon seasonal variation.

Effects of Minor Components of Crude Vegetable Oil on the Enzymatic Method to Analyze Positional Fatty Acid Distributions in Triacylglycerols withCandida antarctica Lipase B

Crude soybean and rapeseed oils were subjected to the method to determine FA distributions in TAG using Candida antarctica lipase B, giving similar results to those for refined oils. Minor components in crude oils, such as percentages of FFA or phospholipids were indicated not to affect 1(3)-selective transesterification by the lipase and FA compositional analysis of the resulting 2-MAG fraction significantly. Phospholipids were confirmed not to contaminate the 2-MAG fraction. Oxidized soybean oil with a PV of 10 meq/kg also gave similar results to the ones for refined oil. The method was confirmed to be applicable for crude oils and oxidized oils with a PV smaller than 10 meq/kg without prior purification of TAG.

Enzymatic Analysis of Positional Fatty Acid Distributions in Triacylglycerols by 1(3)-Selective Transesterification with Candida antarctica Lipase B: a Collaborative Study

The positional distributions of fatty acids (FAs) in fats and oils are principally analyzed by selectively transesterifying the target triacylglycerols (TAGs) at the 1(3) position using Pseudozyma (Candida) antarctica lipase, followed by recovering the resulting 2-monoacylglycerols (MAGs) by chromatography. FA compositions were measured by gas chromatography (GC) after methylating target TAGs and 2-MAGs. The method was collaboratively evaluated by 12 laboratories by analyzing the positional FA distributions in soybean, palm, and sardine oils. The maximum reproducibility relative standard deviations for the major FAs and those at the sn-2 positions of soybean, palm, and sardine oils were 4.41% and 3.92% (18:3n-3), 4.48% and 3.82% (18:0), and 8.93 and 8.24% (14:0), respectively. The values at the sn-2 position were always low. Therefore, these results indicated that the variations were mainly caused by the FA analysis procedure, i.e., the methylation and GC analyses, rather than the enzymatic transesterification and chromatography utilized to prepare 2-MAGs from the target oil.

The Collaborative Study on the Enzymatic Analysis of Positional Distribution of Short- and Medium-chain Fatty Acids in Milk Fat Using Immobilized Candida antarctica Lipase B

The positional distributions of fatty acids (FAs) in milk fat containing short- and medium-chain FAs were analyzed by sn-1(3)-selective transesterification of triacylglycerols (TAGs) with ethanol using immobilized Candida antarctica lipase B (CALB), in a collaborative study conducted by 10 laboratories. The mean C4:0, C6:0, and C8:0 FA contents, when analyzed as propyl esters (PEs) using gas chromatography (GC) with a DB-23 capillary column, were found to be 3.0, 2.0, and, 1.3 area%, respectively. Their reproducibility standard deviations were 0.33, 0.18, and 0.19, respectively. The mean C4:0, C6:0, and C8:0 contents at the sn-2 position were 0.3, 0.4, and 1.0 area%, respectively. Their reproducibility standard deviations were 0.17, 0.11, and 0.19, respectively. The reproducibility standard deviations of C4:0, C6:0, and C8:0 FAs at the sn-2 position were either the same as or smaller than those for milk fat, although the FA contents at the sn-2 position were smaller than those in the milk fat. Therefore, it was concluded that the CALB method for estimating the regiospecific distribution is applicable to TAGs containing short- and medium-chain FAs. When estimating the short-chain (SC) FA contents in fats and oils by GC, it is better to analyze SCFAs as PEs or butyl esters, and not as methyl esters, in order to prevent loss of SCFAs during the experimental procedure because of their volatility and water solubility. This study also revealed that the stationary phase of the GC capillary column affected the flame ionization detector (FID) response of SCFAs. The theoretical FID correction factor (MWFA / active carbon number / atomic weight of carbon) fitted well with the actual FID responses of C4:0-C12:0 FAs when they were analyzed as PEs using a DB-23 column; however, this was not the case when the GC analysis was performed using wax-type columns.

Effects of Regioselectivity and Lipid Class Specificity of Lipases on Transesterification, Exemplified by Biodiesel Production

Lipase-catalyzed ethanolysis of triolein was studied as a model for biodiesel production. Four lipases were immobilized on porous polypropylene, and ethanolysis reactions were carried out in methyl t-butyl ether. The reaction products were analyzed using gas chromatography. Three of the four lipases studied were efficient in the conversion of triolein to 2-monoolein, but slow in the final step of producing glycerol. However, Candida antarctica lipase B was slow in the conversion of triolein, but more efficient in the subsequent two steps than the other lipases. The 1,3-selectivity of the lipases was less pronounced for the monooleins than for triolein. Silica gel was investigated as a catalyst for acyl migration, showing an increase in biodiesel yield with three of the lipases, but a reduction in yield when C. antarctica lipase B was used. The highest biodiesel yield (96 %) was obtained with a combination of Rhizopus arrhizus lipase and C. antarctica lipase B.

The development of flow-through bio-catalyst microreactors from silica micro structured fibers for lipid transformations

This study demonstrates the utility of a flow-through enzyme immobilized silica microreactor for lipid transformations. A silica micro structured fiber (MSF) consisting of 168 channels of internal diameter 4-5 μm provided a large surface area for the covalent immobilization of Candida antartica lipase. The specific activity of the immobilized lipase was determined by hydrolysis of p-nitrophenyl butyrate and calculated to be 0.81 U/mg. The catalytic performance of the lipase microreactor was demonstrated by the efficient ethanolysis of canola oil. The parameters affecting the performance of the MSF microreactor, including temperature and reaction flow rate, were investigated. Characterization of the lipid products exiting the microreactor was performed by non-aqueous reversed-phased liquid chromatography (NARP-LC) with evaporative light scattering detector (ELSD) and by comprehensive two-dimensional gas chromatography (GC x GC). Under optimized conditions of 1 μL/min flow rate of 5 mg/mL trioleoylglycerol (TO) in ethanol and 50 °C reaction temperature, 2-monooleoylglycerol was the main product at > 90% reaction yield. The regioselectivity of the Candida antartica lipase immobilized MSF microreactor in the presence of ethanol was found to be comparable to that obtained under conventional conditions. The ability of these reusable flow-through microreactors to regioselectively form monoacylglycerides in high yield from triacylglycerides demonstrate their potential use in small-scale lipid transformations or analytical lipids profiling.