Synthesis of Structured Phosphatidylcholine Containing n-3 PUFA Residues via Acidolysis Mediated by Immobilized Phospholipase A1

Design and simulation of a caprylic acid enzymatically modified phosphatidylcholine micelle using a coarse-grained molecular dynamics simulations approach

Computationally simulated micelle models provide useful structural information on the molecular and biological sciences. One strategy to study the self-aggregation process of surfactant molecules that make up a micelle is through molecular dynamics (MD) simulations. In this study, a theoretical approach with a coarse-grained MD simulation (CG-MD) was employed to evaluate the critical micellar concentration (CMC), the micellization process, building a tridimensional (3D) model system of a micelle using data from the experimentally enzymatically modified phospholipids (PL) by phospholipase A1 (PA1). This required enzymatic interesterification of soybean phosphatidylcholine (PC) with caprylic acid, along with purification and characterization by chromatographic techniques to measure the esterified fatty acids and the corresponding PL composition. The number of molecules used in the CG-MD simulation system was determined from the experimental CMC data which was 0.025%. The molecular composition of the system is: 1 C 18:2, 2 C 8:0/8:0, 3 C 8:0/18:3n-9, 4 C 8:0/18:0, 5 C8:0/18:2n-6, 6 C8:0/18:1n-9, and 7 C 8:0/16:0. According to our theoretical results, the micelle model is structurally stable with an average Rg of 3.64 ± 0.10 Å, and might have an elliptical form with a radius of 24.6 Å. Regarding CMC value there was a relationship between the experimental data of the modified PLs and the theoretical analysis by GC-MD, which suggest that the enzymatic modification of PLs does not affect their self-aggregation properties. Finally, the micellar system obtained in the current research can be used as a simple and useful model to design optimal biocompatible nanoemulsions as possible vehicles for bioactive small molecules.Communicated by Ramaswamy H. Sarma.

Progress & Prospect of Enzyme-Mediated Structured Phospholipids Preparation

In recent years, structured phospholipids (SPLs), which are modified phospholipids (PLs), have attracted more attention due to their great potential for application in the field of pharmacy, food, cosmetics, and health. SPLs not only possess enhanced chemical, physical and nutritional properties, but also present superior bioavailability in comparison with other lipid forms, such as triacylglycerols, which make SPLs become more competitive carriers to increase the absorption of the specific fatty acids in the body. Compared with chemical-mediated SPLs, the process of enzyme-mediated SPLs has the advantages of high product variety, high substrate selectivity, and mild operation conditions. Both lipases and phospholipases can be used in the enzymatic production of SPLs, and the main reaction type contains esterification, acidolysis, and transesterification. During the preparation, reaction medium, acyl migration, water content/activity, substrates and enzymes, and some other parameters have significant effects on the production and purity of the desired PLs products. In this paper, the progress in enzymatic modification of PLs over the last 20 years is reviewed. Reaction types and characteristic parameters are summarized in detail and the parameters affecting acyl migration are first discussed to give the inspiration to optimize the enzyme-mediated SPLs preparation. To expand the application of enzyme-mediated SPLs in the future, the prospect of further study on SPLs is also proposed at the end of the paper.

Free and Immobilized Lecitase™ Ultra as the Biocatalyst in the Kinetic Resolution of (E)-4-Arylbut-3-en-2-yl Esters

The influence of buffer type, co-solvent type, and acyl chain length was investigated for the enantioselective hydrolysis of racemic 4-arylbut-3-en-2-yl esters using Lecitase™ Ultra (LU). Immobilized preparations of the Lecitase™ Ultra enzyme had significantly higher activity and enantioselectivity than the free enzyme, particularly for 4-phenylbut-3-en-2-yl butyrate as the substrate. Moreover, the kinetic resolution with the immobilized enzyme was achieved in a much shorter time (24–48 h). Lecitase™ Ultra, immobilized on cyanogen bromide-activated agarose, was particularly effective, producing, after 24 h of reaction time in phosphate buffer (pH 7.2) with acetone as co-solvent, both (R)-alcohols and unreacted (S)-esters with good to excellent enantiomeric excesses (ee 90–99%). These conditions and enzyme were also suitable for the kinetic separation of racemic (E)-4-phenylbut-3-en-2-yl butyrate analogs containing methyl substituents on the benzene ring (4b,4c), but they did not show any enantioselectivity toward (E)-4-(4’-methoxyphenyl)but-3-en-2-yl butyrate (4d).

An Efficient Synthesis of Lysophosphatidylcholine Enriched with n-3 Polyunsaturated Fatty Acids by Immobilized MAS1 Lipase

n-3 polyunsaturated fatty acid (PUFA)-rich lysophosphatidylcholine (LPC) with many beneficial effects was effectively synthesized by immobilized MAS1 lipase-catalyzed esterification of n-3 PUFA with sn-glycero-3-phosphatidylcholine (GPC) under vacuum in a solvent-free system. Immobilized MAS1 lipase was found to be a more suitable catalyst for the production of n-3 PUFA-rich LPC when compared with Novozym 435. The maximal GPC conversion and LPC content (93.12% and 90.77 mol %) were obtained under the optimized conditions (enzyme loading of 300 U/g substrate, temperature of 55 °C, and n-3 PUFA/GPC molar ratio of 20:1). Moreover, it was observed that 1-acyl-sn-glycero-3-lysophosphatidylcholine (sn-1 acyl LPC) was the main reaction product, as demonstrated by molecular docking. These results showed that immobilized MAS1 lipase had high phospholipase activity with a predominant specificity for the sn-1 hydroxyl position of GPC to efficiently synthesize highly pure n-3 PUFA-rich LPC from GPC for industrial application.

Lipase Catalyzed Acidolysis for Efficient Synthesis of Phospholipids Enriched with Isomerically Pure cis-9,trans-11 and trans-10,cis-12 Conjugated Linoleic Acid

The production of phospholipid (PL) conjugates with biologically active compounds is nowadays an extensively employed approach. This type of phospholipids conjugates could improve bioavailability of many poorly absorbed active compounds such as isomers of conjugated linoleic acid (CLA), which exhibit versatile biological effects. The studies were carried out to elaborate an efficient enzymatic method for the synthesis of phospholipids with pure (>90%) cis-9,trans-11 and trans-10,cis-12 CLA isomers. For this purpose, three commercially available immobilized lipases were examined in respect to specificity towards CLA isomers in acidolysis of egg-yolk phosphatidylcholine (PC). Different incorporation rates were observed for the individual CLA isomers. Under optimal conditions: PC/CLA molar ratio 1:6; Rhizomucor miehei lipase loading 24% wt. based on substrates; heptane; DMF, 5% (v/v); water activity (aw), 0.11; 45 °C; magnetic stirring, 300 rpm; 48 h., effective incorporation (EINC) of CLA isomers into PC reached ca. 50%. The EINC of CLA isomers was elevated for 25–30% only by adding a water mimic (DMF) and reducing aw to 0.11 comparing to the reaction system performed at aw = 0.23. The developed method of phosphatidylcholine acidolysis is the first described in the literature dealing with isometrically pure CLA and allow to obtain very high effective incorporation.

Optimization of the Synthesis of Structured Phosphatidylcholine with Medium Chain Fatty Acid

Structured phosphatidylcholine was successfully produced by acidolysis between phosphatidylcholine and free medium chain fatty acid, using phospholipase A₁ immobilized on Duolite A568. Response surface methodology was applied to optimize the reaction system using three process parameters: molar ratio of substrates (phosphatidylcholine to free medium chain fatty acid), enzyme loading, and reaction temperature. All parameters evaluated showed linear and quadratic significant effects on the production of modified phosphatidylcholine; molar ratio of substrates contributed positively, but temperature influenced negatively. Increased enzyme loading also led to increased production of modified phosphatidylcholine but only during the first 9 hours of the acidolysis reaction. Optimal conditions obtained from the model were a ratio of phosphatidylcholine to free medium chain fatty acid of 1:15, an enzyme loading of 12%, and a temperature of 45°C. Under these conditions a production of modified phosphatidylcholine of 52.98 % were obtained after 24 h of reaction. The prediction was confirmed from the verification experiments; the production of modified phosphatidylcholine was 53.02%, the total yield of phosphatidylcholine 64.28% and the molar incorporation of medium chain fatty acid was 42.31%. The acidolysis reaction was scaled-up in a batch reactor with a similar production of modified phosphatidylcholine, total yield of phosphatidylcholine and molar incorporation of medium chain fatty acid. Purification by column chromatography of the structured phosphatidylcholine yielded 62.53% of phosphatidylcholine enriched with 42.52% of medium chain fatty acid.

Production of a Health-Beneficial Food Emulsifier by Enzymatic Partial Hydrolysis of Phospholipids Obtained from the Head of Autumn Chum Salmon

Phospholipids and their partial hydrolysates, namely lysophospholipids (LPLs), have been widely used in food, pharmaceutical, and cosmetic products as highly efficient emulsifiers. This study was conducted to produce docosahexaenoic acid (DHA)-esterified LPLs by enzymatic modification of phospholipids obtained from the head of autumn chum salmon (Oncorhynchus keta). The emulsifying properties of the obtained LPLs were also evaluated. Two different types of substrates of salmon head phospholipids were prepared via silica gel and cold acetone precipitation. Enzymatic partial hydrolysis was carried out using immobilized phospholipase A₁ (PLA₁) and Lipozyme RM IM. Results showed that the increase in DHA in the LPLs was much higher in the silica-separated phospholipids than in the acetone-precipitated phospholipids. When silica-separated phospholipids were used as the substrate, the DHA content of the LPLs increased from 23.1% to 40.6% and 42.6% after 8 h of partial hydrolysis with Lipozyme RM IM and immobilized PLA₁, respectively. The yield of the LPLs was comparatively higher in the Lipozyme RM IM than in the immobilized PLA₁ hydrolysis reaction. The critical micelle concentration values of the LPLs and purified lysophosphatidylcholine (LPC) were 100 mg/L and 5 mg/L, respectively. The surface tension values of the LPLs and LPC were reduced to 30.0 mN/m and 30.5 mN/m, respectively. The hydrophilic-lipophilic balance of the LPLs and LPC were 6.0 and 9.4, respectively. Based on the emulsifying properties observed, we conclude that LPLs derived from the phospholipids of salmon head lipids could be used as a health-beneficial emulsifier in the food industry.

Incorportation of Ethyl Esters of EPA and DHA in Soybean Lecithin Using Rhizomucor miehei Lipase: Effect of Additives and Solvent-Free Conditions

The transesterification of soybean lecithin with ethyl esters of polyunsaturated fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) using immobilized lipase from Rhizomucor miehei was tested in the presence or absence of organic solvent (hexane) and additives (urea with Ca(2+) or Mg(2+)). The reaction was carried out at a water concentration of 4 % and ethyl ester to phospholipid mass ratio of 3:1. After 24 h of reaction without solvent or additive, fatty acid incorporation reached 29.1 % and thereafter increased only slightly. After 48 h, incorporation was highest in the presence of Mg(2+), urea, and solvent. After 72 h, it was highest with Mg(2+) and urea in the presence or absence of solvent (56.8 and 45.7 %, respectively). Incorporation of EPA and DHA was thus initially fast without solvent and additive, but was increased after prolonged reaction in the presence of Mg(2+) and urea with or without solvent. These results are innovative and promising since they show that immobilized Rhizomucor miehei lipase has potential as a biocatalyst for interesterification reactions without solvent.

Individual Phosphatidylcholine Species Analysis by RP-HPLC-ELSD for Determination of Polyenylphosphatidylcholine in Lecithins

Polyenylphosphatidylcholine (PPC), a subgroup of the bioactive agents in phosphatidylcholine (PC), has been indicated to possess liver-protective effects. This study aimed to investigate a promising and feasible method to determine PC molecular species with a reverse phase (RP) high-performance liquid chromatograph (HPLC) equipped with an evaporative light scattering detector (ELSD). Chromatography was achieved using a C30 column and an isocratic mobile phase consisting of acetonitrile/methanol/triethylamine (40/58/2, v/v/v) at a flow rate of 1 mL/min, and ELSD detection was performed using 80 °C for the drift tube and an air flow rate of 1.8 L/min. To identify individual peaks on the chromatogram, MALDI-TOF-MS was employed for initial detection, and then the results were used to investigate the relationship between the retention time and fatty acyl chains of each PC molecule. A linear correlation was observed between the retention time and theoretical carbon number (TCN) of individual PC species. The compositions of PC molecular species in soybean and sunflower lecithins were similar to each other, and the major PC molecular species were 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (LLPC), 1-oleoyl-2-linoleoyl-sn-glycero-3-phosphocholine (OLPC), and 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC). The contents of LLPC in soybean PC and sunflower PC were 40.6% and 64.3%, respectively.

Production of structured phosphatidylcholine with high content of DHA/EPA by immobilized phospholipase A₁-catalyzed transesterification

This paper presents the synthesis of structured phosphatidylcholine (PC) enriched with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) by transesterification of DHA/EPA-rich ethyl esters with PC using immobilized phospholipsase A₁ (PLA₁) in solvent-free medium. Firstly, liquid PLA₁ was immobilized on resin D380, and it was found that a pH of 5 and a support/PLA₁ ratio (w/v) of 1:3 were the best conditions for the adsorption. Secondly, the immobilized PLA₁ was used to catalyze transesterification of PC and DHA/EPA-rich ethyl esters. The maximal incorporation of DHA and EPA achieved was 30.7% for 24 h of reaction at 55 °C using a substrate mass ratio (PC/ethyl esters) of 1:6, an immobilized PLA₁ loading of 15% and water dosage of 1.25%. Then the reaction mixture was analyzed by ³¹P nuclear magnetic resonance (NMR). The composition of reaction product included 16.5% PC, 26.3% 2-diacyl-sn-glycero-3-lysophosphatidylcholine (1-LPC), 31.4% 1-diacyl-sn-glycero-3-lysophosphatidylcholine (2-LPC), and 25.8% sn-glycerol-3-phosphatidylcholine (GPC).

Immobilized phospholipase A1-catalyzed modification of phosphatidylcholine with n-3 polyunsaturated fatty acid

n-3 Polyunsaturated fatty acids (n-3 PUFA)-enriched phosphatidylcholine (PC) was successfully produced with fatty acid from fish oil and PC from soybean by immobilized phospholipase A1-catalyzed acidolysis. Detailed studies of immobilization were carried out, and Lewatit VP OC 1600 was selected as a carrier for preparation of immobilized phospholipase A1, which was used for modification of PC by acidolysis. For acidolysis of PC with n-3 PUFA, the effects of several parameters, namely, water content, temperature, and enzyme loading on the reaction time course were investigated to determine optimum conditions. The optimum water content, temperature, and enzyme loading were 1.0%, 55 °C, and 20%, respectively. The highest incorporation (57.4 mol%) of n-3 PUFA into PC was obtained at 24h and the yield of PC was 16.7 mol%. The yield of PC increased significantly by application of vacuum, even though a slight decrease of n-3 PUFA incorporation was observed.