Preparation of medium and long chain triacylglycerols by lipase-catalyzed interesterification in a solvent-free system

A novel synthesis method of medium- and long-chain triglyceride lipids from rubber seed oil catalyzed by enzymatic interesterification and its metabolism mechanism

Medium- and long-chain triglyceride (MLCT) is a striking structural lipid for the supply of energy and essential fatty free acids (FFAs) in the food field. This study aimed to prepare MLCT by enzymatic interesterification of rubber seed oil (RSO) and medium-chain triglyceride (MCT). Fortunately, the conversion of synthesized MLCT could reach 75.4% by the catalysis of Novozym 40086 (7 wt% to MCT) at a temperature of 40 °C with the substrate mole ratio of 1 : 0.7 (RSO : MCT). The as-synthesized MLCT contained unsaturated fatty acid (USFA, 50.13%) at the sn-2 position and exhibited superior performance on the acid value, peroxide value and iodine value in contrast to grade III soybean oil. Moreover, it exhibited the simultaneous release of LCFAs and MCFAs, extremely facilitating the reduction of body weight gain and control of the level of lipids in the blood. Finally, the preferred hepatic metabolism process of the obtained MLCT was proven to be the main cause of the reduced body weight and improved lipid levels by the in vivo deposition experiments. Therefore, our study suggested that the outstanding performance of the MLCT synthesized by RSO in foods as functional lipids.

Medium- and Long-Chain Triacylglycerol: Preparation, Health Benefits, and Food Utilization

Medium- and long-chain triacylglycerol (MLCT) is a structured lipid with both medium- and long-chain fatty acids in one triacylglycerol molecule. Compared with long-chain triacylglycerol (LCT), which is mainly present in common edible oils, and the physical blend of medium-chain triacylglycerol with LCT (MCT/LCT), MLCT has different physicochemical properties, metabolic characteristics, and nutritional values. In this article, the recent advances in the use of MLCT in food formulations are reviewed. The natural sources and preparation of MLCT are discussed. A comprehensive summary of MLCT digestion, absorption, transport, and oxidation is provided as well as its health benefits, including reducing the risk of overweight, hypolipidemic and hypoglycemic effects, etc. The potential MLCT uses in food formulations, such as infant formulas, healthy foods for weight loss, and sports foods, are summarized. Finally, the current safety assessment and regulatory status of MLCT in food formulations are reviewed.

Bioimprinted lipase-catalyzed synthesis of medium- and long-chain structured lipids rich in docosahexaenoic acid for infant formula

Medium- and long-chain structured lipids (MLSLs) rich in docosahexaenoic acid (DHA) were obtained in shorter reaction time by acidolysis of single-cell oil (DHASCO) from Schizochytrium sp. with caprylic acid (CA) using a lipase bioimprinted with fatty acids as a catalyst. The conditions for preparation of the bioimprinted lipase for the acidolysis reaction were firstly optimized and the activity of the obtained lipase was 2.17 times higher than that of the non-bioimprinted. The bioimprinted lipase was then used as a catalyst and the reaction conditions were optimized. Under the optimal conditions, the equilibrium could be achieved in 4 h, and the total and sn-1,3 CA contents in the product were 29.18% and 42.34%, respectively, and the total and sn-2 DHA contents were 46.26% and 70.12%, respectively. Such MLSLs rich in sn-1,3 CA and sn-2 DHA are beneficial for DHA absorption, and thus have potential for use in infant formula.

Preparation of functional oils rich in diverse medium and long-chain triacylglycerols based on a broadly applicable solvent-free enzymatic strategy

To address the problems of long reaction times and limited range of adaptation in enzymatic synthesis medium- and long-chain triacylglycerols (MLCTs), a broadly applicable solvent-free enzymatic interesterification strategy was proposed. Candida sp. lipase (CSL) was immobilized on hydrophobic hollow mesoporous silica spheres (HHSS) to construct a biocatalyst designated as CSL@HHSS with a 15.3 % immobilization yield and a loading amount of 94.0 mg/g. The expressed activity and the specific activity were 20.14 U/g and 173.62 U/g, which were 4.6 and 5.6 times higher than that of free CSL, respectively. This biocatalyst demonstrated higher activity, wider applicability, and excellent reusability. Linseed oil, sunflower oil, perilla seed oil, algal oil, and malania oleifera oil were applied as substrates to produce MLCTs with medium-chain triacylglycerols (MCT) catalyzed by CSL@HHSS through interesterification in yields ranging from 69.6 % to 78.0 % within 20 min. Specific fatty acids, including linolenic acid, oleic acid, DHA, and nervonic acid (the first reported), were introduced into MLCT's skeleton, respectively. The structures were finely analyzed and identified by GC and UPLC-MS. The catalytic efficiency value of CSL@HHSS in catalyzing interesterification between linseed oil and MCT (70 ℃, 20 min, lipase 6 wt%) is 0.86 g/g∙min, which is the highest ever reported. This paper presents an effective and sustainable strategy for functional MLCTs production.

Intensified synthesis of a triglyceride of octanoic acid using sonication and assessment of its frying characteristics

Intensification in synthesis of triglycerides of octanoic acid using a heterogeneous amberlyst-15 catalyst has been investigated with the application of ultrasound under solvent-free conditions. Further, the frying characteristics of medium-chain triglycerides (tricaprin) are evaluated by deep frying of French fries in various combinations of palm oil and tricaprin. Understanding into the effect of parameters such as the temperature of the reaction (over the range of 40 °C-80 °C), loading of amberlyst-15 (1%-5%) and molar ratio of fatty acid to glycerol (3:1-3:5) along with the ultrasound conditions as duty cycle (40%-90%) and time on the conversion (%) has also been developed. Based on the outcomes of the study, optimum reaction conditions seen are 3:4 as the molar ratio of fatty acid (C8): glycerol, amberlyst-15 loading of 3% and a reaction temperature of 50 °C. It was further observed that the optimum ultrasound conditions required for maximum conversion of 99.8% were 240 W power, 80% duty cycle and 15 min as the ultrasound irradiation time. Under similar conditions, the conventional synthesis resulted in only 20% conversion in 15 min. Reusability studies also established that the acid-resin catalyst was effectively reused for 8 times. The PV, p-AV and TPC of frying oil combination containing higher tricaprin (50:50-palm oil: MCT) was 8.4 ± 0.8, 23.1 ± 0.01 and 29.8 ± 0.01 respectively, which were lowest as compared with other blends indicating the beneficial effects of MCT in frying applications. The work clearly shows that the ultrasound application for the synthesis of triglyceride of octanoic acid gives higher conversion (%) in a less time and also demonstrates that MCT could be a good alternative for deep frying of foods in combination with palm oil to enhance the shelf-life of food.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-022-05379-3.

Ultrasound enhanced butyric acid-lauric acid designer lipid synthesis: Based on artificial neural network and changes in enzymatic structure

Ultrasound is a green technology for intensifying enzymatic reactions. In this study, an ultrasonic water bath with equipment parameters of 28 kHz, 1750.1 W/m², 60% duty cycle was used to assist the synthesis of butyric acid-lauric acid designer lipid (BLDL), which was catalyzed by Lipozyme 435. A convincing three-layer feed-forward artificial neural network (ANN) model was established (R² = 0.949, RMSE = 4.759, ADD = 7.329) to accurately predict the optimal parameters combination, which was described as 13.72 mL reaction volume, 15.49% enzyme loading, 0.253 substrate molar ratio (tributyrin/lauric acid), 56.58 °C reaction temperature and 120 min reaction time. The ultrasonic assistance increased actual butyric acid conversion rate by 11.38%, and also enhanced the consumption rate of tributyrin and lauric acid during the reaction. Meanwhile, the esterification activity of Lipozyme 435 was enhanced and its effectiveness up to 6 cycles. Structurally, ultrasound assistance significantly disrupted the secondary structure of the Lipozyme 435: reduced the content of α-helices, increased the content of β-sheet and β-turn. In addition, sonication caused an increase in crevice and micro-damage on the surface of the immobilized enzyme. In conclusion, low-intensity ultrasound at 28 kHz improved the synthesis efficiency of BLDL, which was scientifically predicted by ANN model, and the change of enzyme structure may be the vital reason for ultrasound enhanced reaction. However, the effect of ultrasound on immobilized enzymes' activity needs to be further explored.

Triglycerides of medium-chain fatty acids: a concise review

Medium-chain triglycerides contain medium-chain fatty acid esterified to the glycerol backbone. These MCFA have a shorter chain length and are quickly metabolized in the body serving as an immediate energy source. They are known to have good physiological as well as functional characteristics which help in treating various health disorders. Naturally, they are found in coconut oil, milk fat, and palm kernel oil, and they are synthetically produced by esterification and interesterification reactions. Due to their numerous health benefits, MCT is used as a functional or nutraceutical oil in various food and pharmaceutical formulations. To increase their nutraceutical benefits and food applications MCFA can be used along with polyunsaturated fatty acids in the synthesis of structured lipids. This review aims to provide information about triglycerides of MCFA, structure, metabolism, properties, synthetic routes, intensified synthesis approaches, health benefits, application, and safety of use of MCT in the diet.

Medium chain triglycerides (MCT): State-of-the-art on chemistry, synthesis, health benefits and applications in food industry

Medium chain triglycerides (MCT) are esters of fatty acids with 6 to 12 carbon atom chains. Naturally, they occur in various sources; their composition and bioactivity are source and extraction process-linked. The molecular size of MCT oil permits unique metabolic pathways and energy production rates, making MCT oil a high-value functional food. This review details the common sources of MCT oil, presenting critical information on the various approaches for MCT oil extraction or synthesis. Apart from conventional techniques, non-thermal processing methods that show promising prospects are analyzed. The biological effects of MCT oil are summarized, and the range of need-driven modification approaches are elaborated. A section is devoted to highlighting the recent trends in the application of MCT oil for food, nutraceuticals, and allied applications. While much is debated about the role of MCT oil in human health and wellness, there is limited information on daily requirements, impact on specific population groups, and effects of long-term consumption. Nonetheless, several studies have been conducted and continue to identify the most effective methods for MCT oil extraction, processing, handling, and storage. A knowledge gap exists and future research must focus on technology packages for scalability and sustainability.

Medium and long-chain structured triacylglycerol enhances vitamin D bioavailability in an emulsion-based delivery system: combination of in vitro and in vivo studies

Vitamin D (VitD) is an essential fat-soluble micronutrient required for maintaining and regulating calcium homeostasis. Although sunlight can provide VitD, epidemiological studies indicate that the occurrence of VitD deficiency and insufficiency is widespread. Lipids are required at all stages of VitD digestion and absorption. In this research two different medium and long-chain triacylglycerol structures, possessing identical fatty acid composition lipids, namely structured triacylglycerol (STG), and physical mixtures of medium/long-chain triacylglycerol (MCT/LCT), were selected. Our results demonstrated that STG had a significant VitD bioavailability compared to MCT/LCT. In terms of the lipid digestion and absorption, the extent of the higher free fatty acid released (69.42%, p < 0.05), extent of lipolysis (89.28%, p < 0.05), lipolysis rate (0.06 s^-1, p < 0.05), and the ratio of the long-chain fatty acid to medium-chain fatty acid of STG (4.8, p < 0.05), result in a higher capacity for accommodating VitD when forming mixed micelles (61.31%, p < 0.05). An in vivo animal study also demonstrated that STG significantly increases the delivery ability of VitD (18.75 ng mL^-1, p < 0.05). The findings of this work may have unique applications for designing novel interesterified lipids with an effective delivery capacity for fat-soluble nutrients.

Distigmasterol-Modified Acylglycerols as New Structured Lipids-Synthesis, Identification and Cytotoxicity

Plant sterols, also referred as phytosterols, have been known as bioactive compounds which have cholesterol-lowering properties in human blood. It has been established that a diet rich in plant sterols or their esters alleviates cardiovascular diseases (CVD), and also may inhibit breast, colon and lung carcinogenesis. Phytosterols, in their free and esterified forms, are prone to thermo-oxidative degradation, where time and temperature affect the level of degradation. Looking for new derivatives of phytosterols with high thermo-oxidative stability for application in foods, our idea was to obtain novel structured acylglycerols in which two fatty acid parts are replaced by stigmasterol residues. In this work, asymmetric (1,2- and 2,3-) distigmasterol-modified acylglycerols (dStigMAs) were synthesized by the covalent attachment of stigmasterol residues to sn-1 and sn-2 or sn-2 and sn-3 positions of 3-palmitoyl-sn-glycerol or 1-oleoyl-sn-glycerol, respectively, using a succinate or carbonate linker. The chemical structures of the synthesized compounds were identified by NMR, HR-MS, and IR data. Moreover, the cytotoxicity of the obtained compounds was determined. The dStigMAs possessing a carbonate linker showed potent cytotoxicity to cells isolated from the small intestine and colon epithelium and liver, whereas the opposite results were obtained for compounds containing a succinate linker.

Argan Oil as a Rich Source of Linoleic Fatty Acid for Dietetic Structured Lipids Production

Argan oil is rich in long-chain unsaturated fatty acids (FA), mostly oleic and linoleic, and natural antioxidants. This study addresses the production of low-calorie structured lipids by acidolysis reaction, in a solvent-free system, between caprylic (C8:0; system I) or capric (C10:0; system II) acids and argan oil, used as triacylglycerol (TAG) source. Three commercial immobilized lipases were tested: Novozym^® 435, Lipozyme^® TL IM, and Lipozyme^® RM IM. Higher incorporation degree (ID) was achieved when C10:0 was used as acyl donor, for all the lipases tested. Lipozyme^® RM IM yielded the highest ID for both systems (28.9 ± 0.05 mol.% C10:0, and 11.4 ± 2.2 mol.% C8:0), being the only catalyst able to incorporate C8:0 under the reaction conditions for biocatalyst screening (molar ratio 2:1 FA/TAG and 55 °C). The optimal conditions for Lipozyme^® RM IM in system II were found by response surface methodology (66 °C; molar ratio FA/TAG of 4:1), enabling to reach an ID of 40.9 mol.% of C10:0. Operational stability of Lipozyme^® RM IM in system II was also evaluated under optimal conditions, after eight consecutive 24 h-batches, with biocatalyst rehydration between cycles. The biocatalyst presented a half-life time of 103 h.

Medium chain triglyceride and medium-and long chain triglyceride: metabolism, production, health impacts and its applications - a review

Structured lipid is a type of modified form of lipid that is "fabricated" with the purpose to improve the nutritional and functional properties of conventional fats and oils derived from animal and plant sources. Such healthier choice of lipid received escalating attention from the public for its capability to manage the rising prevalence of metabolic syndrome. Of which, medium-chain triacylglycerol (MCT) and medium-and long-chain triacylglycerol (MLCT) are the few examples of the "new generation" custom-made healthful lipids which are mainly composed of medium chain fatty acid (MCFA). MCT is made up exclusively of MCFA whereas MLCT contains a mixture of MCFA and long chain fatty acid (LCFA), respectively. Attributed by the unique metabolism of MCFA which is rapidly metabolized by the body, MCFA and MCT showed to acquire multiple physiological and functional properties in managing and reversing certain health disorders. Several chemically or enzymatically oils and fats modification processes catalyzed by a biological or chemical catalyst such as acidolysis, interesterification and esterification are adopted to synthesis MCT and MLCT. With their purported health benefits, MCT and MLCT are widely being used as nutraceutical in food and pharmaceutical sectors. This article aims to provide a comprehensive review on MCT and MLCT, with an emphasis on the basic understanding of its structures, properties, unique metabolism; the current status of the touted health benefits; latest routes of production; its up-to-date applications in the different food systems; relevant patents filed and its drawbacks.

Enzymatic synthesis of structured lipids from grape seed (Vitis vinifera L.) oil in associated packed bed reactors

Triacylglycerols (TAGs) can be modified to increase the absorption of fatty acids, prevent obesity, and treat fat malabsorption disorders and metabolic diseases. Medium-long-medium (MLM)-type TAGs, which contain medium-chain fatty acids in the sn-1 and sn-3 positions of the glycerol backbone and a long-chain fatty acid in the sn-2 position, show particularly interesting nutritional characteristics. This study aimed to synthesize MLM-type TAGs by enzymatic acidolysis of grape seed oil with medium-chain capric acid (C10:0) in associated packed bed reactors. The reaction was carried out during 120 H, at 45 °C, using lipase from Rhizomucor miehei (Lipozyme^® RM IM). The residence time distribution of reagents in the reactor was quantified to evaluate the reactor behavior and to diagnose the existence of preferential paths. The reaction progress was monitored by analyzing TAG composition and, at the steady state (after 48 H of reaction), the incorporation degree achieved a value of 39.91 ± 2.77%. To enhance the capric acid incorporation, an acidolysis reaction in associated packed bed reactors was performed. The results showed a good operational stability of the biocatalyst, revealing values of half-life 209.64 H, 235.63 H of packed bed and associated packed bed reactor, respectively, and a deactivation coefficient 0.0061 H^-1.

Lipase catalysis of α-linolenic acid-rich medium- and long-chain triacylglycerols from perilla oil and medium-chain triacylglycerols with reduced by-products

BACKGROUND

Medium- and long- chain triacylglycerols (MLCTs) are functional structural lipids that can provide the human body with essential fatty acids and a faster energy supply. This study aimed to prepare MLCTs rich in α-linolenic by enzymatic interesterification of perilla oil and medium-chain triacylglycerols (MCTs), catalyzed by Lipozyme RM IM, Lipozyme TL IM, Lipozyme 435, and Novozyme 435 respectively.

RESULTS

The effects of lipase loading, concentration of MCTs, reaction temperature, and reaction time on the yield of MLCTs were investigated. It was found that the reaction achieved more than a 70% yield of MLCTs in triacylglycerols under the conditions of 400 g kg^-1 MCTs and 60 g kg^-1 lipase loading after equilibrium. A novel two-stage deodorization was also applied to purify the interesterification products. The triacylglycerols reach over 97% purity in the products with significant removal (P < 0.05) of the free fatty acids, and the trans fatty acids were strictly controlled at below 1%. There was more than 40% α-linolenic in the purified products, with long-chain fatty acids mostly occupying the desired sn-2 position in acylglycerols, which are more active in hydrolysis.

CONCLUSION

A series of novel α-linolenic acid-rich medium- and long-chain triacylglycerols was prepared. Under appropriate reaction conditions, the yield of MLCTs in triacylglycerols was above 70%. A novel two-stage deodorization can be used to promote the elimination of free fatty acids and limit the generation of trans fatty acids. © 2020 Society of Chemical Industry.

Ultrasonic Pretreatment in Synthesis of Caprylic-Rich Structured Lipids by Lipase-Catalyzed Acidolysis of Corn Oil in Organic System and Its Physicochemical Properties

The current work was to evaluate the lipase-catalyzed acidolysis of corn oil with caprylic acid (CA) in organic system under bath ultrasonic pretreatment and to analyze the physicochemical properties of structured lipids (SLs). Under optimum conditions (Novozym 40086 lipase, 200 W ultrasound power, 10 min ultrasound pretreatment time, 12% dosage of lipase, Triacylglycerol (TAG)/Free fatty acids (FFA): 1/8, 40 °C for 6 h), a 45.55% CA incorporation was obtained (named SLs-U). The highest CA incorporation was 32.75% for conventional method at reaction time of 10 h (named SLs-N). The predominant TAG types of SLs were MLM (medium-, long- and medium-chain-type TAGs) and MLL (medium-, long- and long-chain-type TAGs). X-ray diffraction analysis revealed that both SLs-U and SLs-N present β form. Differential scanning calorimetry (DSC) analysis showed that both SLs-U and SLs-N show a lower melting and crystallization temperature than corn oil. This study suggested that bath ultrasonic pretreatment can accelerate lipase-catalyzed acidolysis synthesis of MLM structured lipids in an organic system, and two kinds of structured lipids show similar physicochemical properties.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

Monitoring the Activity of Immobilized Lipase with Quinizarin Diester Fluoro-Chromogenic Probe

Quinizarin diester is used as a fluoro-chromogenic substrate of the activity of lipase supported in poly(methylmetacrylate) beads (CALB, Novozym^® 435) dispersed in organic solvents. The monoester and diester of quinizarin are both non-fluorescent species contrasting with the enzymatic product quinizarin that shows optical absorption in the visible region and strong fluorescence signal. The enzymatic conversion is accomplished by spectroscopic measurements and it follows a sigmoid curve from which the mean reaction time of the enzymatic process can be determined. This parameter indicates the enzyme activity of the immobilized lipase. Its dependency with the amount of lipase allowed the determination of the ratio of the catalytic rate and the Michaelis constant (k_c/K_m) and the experimental value found was (1.0 ± 0.1) × 10⁻² mg⁻¹/min in the case of quinizarin diacetate.