Composition and Structure of Single Cell Oil Produced by Schizochytrium limacinum SR31

Enzymatic Synthesis of Structured Lipids Enriched with Medium- and Long-Chain Triacylglycerols via Pickering Emulsion-Assisted Interfacial Catalysis: A Preliminary Exploration

Medium- and long-chain triacylglycerol (MLCT), as a novel functional lipid, is valuable due to its special nutritional properties. Its low content in natural resources and inefficient synthesis during preparation have limited its practical applications. In this study, we developed an effective Pickering emulsion interfacial catalysis system (PE system) for the enzymatic synthesis of MLCT by trans-esterification. Lipase NS 40086 served simultaneously as a catalyst and a solid emulsifier to stabilize the Pickering emulsion. Benefitting from the sufficient oil-water interface, the obtained PE system exhibited outstanding catalytic efficiency, achieving 77.5% of MLCT content within 30 min, 26% higher than that of a water-free system. The Km value (0.259 mM) and activation energy (14.45 kJ mol-1) were 6.8-fold and 1.6-fold lower than those of the water-free system, respectively. The kinetic parameters as well as the molecular dynamics simulation and the tunnel analysis implied that the oil-water interface enhanced the binding between substrate and lipase and thus boosted catalytic efficiency. The conformational changes in the lipase were further explored by FT-IR. This method could give a novel strategy for enhancing lipase activity and the design of efficient catalytic systems to produce added-value lipids. This work will open a new methodology for the enzymatic synthesis of structured lipids.

Medium- and long-chain triacylglycerols and di-unsaturated fatty acyl-palmitoyl-glycerols in Chinese human milk: Association with region during the lactation

The triacylglycerols (TAGs) of medium- and long-chain triacylglycerols (MLCT) and di-unsaturated fatty acyl-palmitoyl-glycerols (UPU) in human milk provide better nutritional effects, and should be prioritized as crucial focuses on neonatal nutrition research. However, little has been done on the influences of the lactation stage and regional diversity on MLCT and UPU. In this study, we collected 204 human milk samples during colostrum, 1st and 4th month from the north (Baotou), central (Beijing), east (Jinan), southwest (Kunming), southeast (Shenzhen), and northwest (Xining) regions of China. There were 122 species of TAGs detected with UPLC-Q-TOF-MS, including 60 kinds of MLCT and 15 kinds of UPU. The MLCT and UPU type TAGs in human milk were ~27 and ~38%, respectively. The sum content of MLCT and UPU in human milk was stable. Compared to the regional diversity, lactation stages showed more obvious influences on MLCT and UPU composition. Moreover, a summary of TAG studies indicated that Chinese human milk showed a higher ratio of O-P-L to O-P-O than in western countries.

Digestion of Medium- and Long-Chain Triacylglycerol and sn-2 Palmitate in Infant Formula: A Study Based on Dynamic In Vitro Simulation of Infant Gastrointestinal Lipolysis

In this study, lipolysis of triacylglycerols (TAGs) in infant formula (IF) composed of different oils and supplied with different structured TAGs, including medium- and long-chain triacylglycerol (MLCT) and sn-2 palmitate, was studied using a dynamic digestion model simulating the infant gastrointestinal tract. The molecular species of digestion products released during digestion, including diacylglycerols, monoacylglycerols (MAGs), and free fatty acids, as well as undigested TAGs, were identified and quantified using liquid chromatography-mass spectrometry. We observed clearly different lipolysis degrees (LDs), with diversity in digestion products of different IFs. IFs supplied with MLCT showed moderate medium-chain fatty acid release during gastric digestion and higher LD after intestinal digestion. The presence of sn-2 palmitate in IF was associated with higher content of MAG-16:0 in digestion products. The species and contents of digestion products in IF were highly influenced by structured TAGs.

Evaluation of total, sn-2 fatty acid, and triacylglycerol composition in commercial infant formulas on the Chinese market: A comparative study of preterm and term formulas

Preterm infants with physiological immaturity require higher lipid provision than term infants. This study compared the lipid composition, including total, sn-2 fatty acid, and triacylglycerol (TAG) compositions in 14 preterm formulas and 25 term formulas in the Chinese market, in 2020-2021. Preterm formula had higher medium-chain fatty acid (MCFA) and comparable C22:6n-3 (DHA) contents than term formula. Notably, significantly lower C16:0 and C18:0 (p < 0.001) were distributed on the sn-2 position in preterm formula. Two hundred and thirteen kinds of TAG molecular species were identified using UPLC-Q-TOF-MS. In preterm formula, significantly higher Ca-Ca-Cy and Ca-Ca-Ca (p < 0.001) existed. These clear distinctions showed the challenge of the progress in preterm formula, such as DHA status, MCFA pattern, and TAG esterified with palmitic acid on the sn-2 position.

The enzymatic synthesis of EPA-rich medium- and long-chain triacylglycerol improves the digestion behavior of MCFA and EPA: evidence on in vitro digestion

Medium-chain triglyceride (MCT) and eicosapentaenoic acid (EPA) have been widely applied in nutritional supplementation. However, when administered individually or mixed, they were unable to maximize their nutritional value. Hence, EPA-rich medium- and long-chain triacylglycerol (MLCT) was synthesized from MCT and EPA-rich fish oil (FO) by enzymatic transesterification. The fatty acids in triglyceride (TAG) were rearranged which resulted in significant changes in TAG profiles compared to the physical mixture of MCT and FO (PM). EPA-containing MML (MML, MLM and LMM) and LLM (LLM, LML and MLL) type TAGs account for 70.21%. The fate of different oils (MCT, FO, PM, and MLCT) across the gastrointestinal tract was subsequently simulated using an in vitro digestion model. The results showed that the physical and structural characteristics of different oils during digestion depended upon the oil type and the microenvironment they were in. After 120 min of small intestine digestion, the degree of hydrolysis for MLCT was higher than that for the other three oils. The final FFA release level was in the following order: MLCT (102.79%) > MCT (95.20%) > PM (85.81%) > FO (74.18%). This can be attributed to the composition and positional distribution of fatty acids in TAGs. What's more, LCFAs (EPA) in MLCT mainly existed in the form of sn-2 MAG, which was conducive to their subsequent absorption and transport. These results may aid in the future rational design of structural lipids, thereby regulating lipid digestion and maximizing the nutritional value of oils.

Production of polyunsaturated fatty acids by Schizochytrium (Aurantiochytrium) spp

Diverse health benefits are associated with dietary consumption of omega-3 long-chain polyunsaturated fatty acids (ω-3 LC-PUFA), particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Traditionally, these fatty acids have been obtained from fish oil, but limited supply, variably quality, and an inability to sustainably increase production for a rapidly growing market, are driving the quest for alternative sources. DHA derived from certain marine protists (heterotrophic thraustochytrids) already has an established history of commercial production for high-value dietary use, but is too expensive for use in aquaculture feeds, a much larger potential market for ω-3 LC-PUFA. Sustainable expansion of aquaculture is prevented by its current dependence on wild-caught fish oil as the source of ω-3 LC-PUFA nutrients required in the diet of aquacultured animals. Although several thraustochytrids have been shown to produce DHA and EPA, there is a particular interest in Schizochytrium spp. (now Aurantiochytrium spp.), as some of the better producers. The need for larger scale production has resulted in development of many strategies for improving productivity and production economics of ω-3 PUFA in Schizochytrium spp. Developments in fermentation technology and metabolic engineering for enhancing LC-PUFA production in Schizochytrium spp. are reviewed.

Highly efficient synthesis of 4,4-dimethylsterol oleates using acyl chloride method through esterification

In this study, the 4,4-dimethylsterol oleates were efficiently synthesized through esterification of 4,4-dimethylsterols and oleoyl chloride. The impact of reaction parameters on the 4,4-dimethylsterol conversion were investigated. The 4,4-dimethylsterol conversion increased with pyridine dosage, molar ratio of oleoyl chloride to 4,4-dimethylsterols, and temperature. The highest conversion of 99.27% was obtained with molar ratio of 1.1:1 at 313 K for 60 min. A second-order kinetic model describing acyl chloride esterification featuring high correlation coefficients was established. Arrhenius-Van't Hoff plot suggested activation energy and pre-exponential factor were 15.54 kJ mol^-1 and 1.78 × 10³ L mol^-1 min^-1, respectively. The molecular structure of 4,4-dimethylsterol oleates were finally identified by attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR), ultra-performance liquid chromatography system coupled with quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS), and nuclear magnetic resonance (NMR).

The Triacylglycerol Profile of Oil Bodies and Oil Extracted from Argania spinosa Using the UPLC Along with the Electrospray Ionization Quadrupole-Time-of-Flight Mass Spectrometry (LC-Q-TOF-MS)

The triacylglycerol (TAG) matrix of argan oil (AO) bodies (AOB) along with the TAGs of AO extracted from the same kernels using an organic solvent, were identified and quantified using the ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Generally, both samples showed a similar TAGs profile but AO found to have three extra TAGs in low amount. In total 23 and 26 different TAGs were identified in AOBs and AO, respectively. The most abundant TAGs were OOL, POO, OOO, and POL in both samples. Furthermore, oleic acid, linoleic acid, and palmitic acid were the major fatty acids in both AOBs and AO. To the best of our knowledge, this is the first research that studied the TAGs matrix of an oil body revealing no major difference between the TAGs profile protected by the AOBs membrane and the oil extracted from the whole seed. PRACTICAL APPLICATION: Seed and kernels oil bodies emulsion tend to be the new source of emulsified oil in food and cosmetic industries. However, before replacing a product with another, we have to make sure that the new alternative can offer better or at least similar benefits. Our results showed that the triacylglycerols (TAGs) matrix and the argan oil (AO) share the same TAGs profile with a relatively close percentage. Therefore, AO bodies can be the perfect pre-emulsified oil for some food products like sauces and creams.

Evaluation of sn-2 fatty acid composition in commercial infant formulas on the Chinese market: A comparative study based on fat source and stage

The sn-2 fatty acid composition of 180 commercial infant, follow-on and growing-up formulas with three fat sources (plant oil, cows' milk and goats' milk) was investigated and compared with mature human milk (MHM). Sn-2 fatty acids in formulas were mostly dependent on fat source and stage. Compared with MHM, all types of formulas contained lower levels of palmitic acid (PA), saturated fatty acid and long-chain polyunsaturated fatty acids (LC-PUFA), and higher levels of oleic acid (OA), linoleic acid (LA) and α-linolenic acid (LNA) at the sn-2 position. Even some formulas were supplemented with 1,3-dioleoyl-2-palmitoylglycerol, the proportions of relative PA at the sn-2 position in formulas were much lower than that in MHM. Moreover, formulas had higher proportions of relative OA, LA and LNA, and lower LC-PUFAs at the sn-2 position. This study indicated that there were significant differences in the positional distribution of fatty acids between formulas and MHM.

Production of sn-1,3-distearoyl-2-oleoyl-glycerol-rich fats from mango kernel fat by selective fractionation using 2-methylpentane based isohexane

High-purity isohexane containing 88.12% 2-methylpentane, which has a higher polarity than industrial hexane, was selected to selectively fractionate mango kernel fat to produce 1,3-distearoyl-2-oleoyl-glycerol (SOS)-rich fat. The three-stage fractionation process was optimized by considering the stearin yield and its SOS content to obtain a third stearin (TS). This fat contained a high percentage of SOS (69.2%) with only 0.8% diacylglycerol. Mass spectra and sn-2 fatty acid analyses further revealed that the TS was mainly composed of symmetrical monounsaturated triacylglycerols. Compared with cocoa butter (CB), the unique composition of the TS improved its thermal properties (35.6% and 0% solid fat content at 35°C for the TS and CB, respectively). In particular, tempered binary fat blends, which were composed of 20-50% TS and 50-80% CB, showed acceptable compatibility at 20-28°C. The TS could be utilized by chocolate manufacturers to make products suitable for sale and consumption in tropical conditions.