Interesterification kinetics of triglycerides and fatty acids with modified lipase inn-hexane

The kinetics of lipase-catalyzed interesterification of triglycerides and fatty acids in organic media was studied. First, the lipase Saiken 100,Rhizopus japonicus, was modified by surfactant to form an enzyme precipitate in aqueous solution, which was well dispersed in organic solvents. This modified lipase catalyzed the interesterification of tripalmitin and stearic acid. The enzyme has 1,3-positional specificity and does not distinguish between stearic and palmitic acids. The kinetic model developed to describe the interesterification reaction system is based on mass balance of two consecutive second-order reversible reactions. The reaction rate constant, k, was determined by solving the differential rate equations of the reaction system and by expressing the value of k as a function of concentrations of the substrates with time. The model gave satisfactory results. The best value of the specific reaction rate constant k* that fits all experimental data was 1.2 · 10⁻⁵ [L²/(mmol · mg biocatalyst · h)] under the reaction conditions in this study.     

A Novel Lipase from Lasiodiplodia theobromae Efficiently Hydrolyses C8-C10 Methyl Esters for the Preparation of Medium-Chain Triglycerides’ Precursors

Medium-chain triglycerides (MCTs) are an emerging choice to treat neurodegenerative disorders such as Alzheimer’s disease. They are triesters of glycerol and three medium-chain fatty acids, such as capric (C8) and caprylic (C10) acids. The availability of C8–C10 methyl esters (C8–C10 ME) from vegetable oil processes has presented an opportunity to use methyl esters as raw materials for the synthesis of MCTs. However, there are few reports on enzymes that can efficiently hydrolyse C8–C10 ME to industrial specifications. Here, we report the discovery and identification of a novel lipase from Lasiodiplodia theobromae fungus (LTL1), which hydrolyses C8–C10 ME efficiently. LTL1 can perform hydrolysis over pH ranges from 3.0 to 9.0 and maintain thermotolerance up to 70 °C. It has high selectivity for monoesters over triesters and displays higher activity over commercially available lipases for C8–C10 ME to achieve 96.17% hydrolysis within 31 h. Structural analysis by protein X-ray crystallography revealed LTL1’s well-conserved lipase core domain, together with a partially resolved N-terminal subdomain and an inserted loop, which may suggest its hydrolytic preference for monoesters. In conclusion, our results suggest that LTL1 provides a tractable route towards to production of C8–C10 fatty acids from methyl esters for the synthesis of MCTs.     

Molecular interaction of triglycerides on a modified silica (Kieselguhr G): a thermodynamical approach by surface tension calculation and DSC measurements

Peanut and linseed oils were drained vertically on thin layers, made of either native, hydrophilic or hydrophobic Kieselguhr G (silica), in order to get information on the interactions that may occur between triglycerides (TGs) and the filtering material. Except for hydrophobic silica, a partition of the TGs as function of the distance run was observed. Highly‐unsaturated TGs were concentrated at the starting point of the running distance and distances between fractions grew larger with the hydrophobicity of the silica. Surface tension components of silica were calculated: whereas Van Oss' method could not discriminate between hydrophilic and hydrophobic Kieselguhr G, Chibowski's method differentiated both compounds by a higher electron donor component (γ) in hydrophilic silica. Calorimetric studies of pure TGs interacting with Kieselguhr G discriminated between saturated TGs exhibiting a lower melting temperature as they interacted with the support, and unsaturated TG having a higher melting temperature. It is concluded that electron densities are involved in interactions occurring between TGs and silica, i.e. high unsaturation number and high γ component.     

Organotypic co-culture system to study plant extract bioactivity on hepatocytes

Natural plant extracts are complex mixtures of molecules that have to be uptaken and metabolized, at least by the intestinal barrier, before they reach their body targets. This paper evaluates the feasibility of using a co-culture system to assay the bioactivity of plant extract on hepatic cells closest to the in vivo situation. Caco-2 cells, mimicking intestinal barrier roles, were grown on inserts on a monolayer of HepG2 hepatocytes for 24 h. The co-culture induced some adaptations, but the Caco-2 cells showed no differences in their abilities to filter and metabolize grape-seed derived extract (GSPE) components. The co-culture clearly reproduced the ability of a procyanidin extract to decrease the triglyceride secretion of hepatocytes, a proven in vivo effect. This system mimics a human physiological system that is useful for assaying the bioactivity of extracts and may be able to be used for developing new functional foods.     

Exploratory chemometric analysis for the characterisation of Tunisian olive cultivars according to their lipid and sterolic profiles

This study aims to evaluate some Tunisian olive genetic resources using fatty acid, triacyglycerol and sterolic compositions and to classify the cultivars according to their fruit genotype and to their respective geographical origin (North, Centre and South). manova results showed that the studied cultivars presented highly significant differences regarding all the variables (P < 0.01). The most discriminant variables of fatty acids are C17:1 (F = 98.468), C16:0 (F = 92.994), C18:1 (F = 60.865), C18:1/C18:2 (F = 44.632) and C18:2 (F = 40.167); those of triacylglycerols are POP (F = 123.34), LLL (F = 122.944), LnLO (F = 98.363), POO (F = 93.357) and LOO (F = 90.42), while sitostanol (F = 289.171), campestanol (F = 192.792) and campesterol (F = 160.724) have the higher discriminant power among sterol compounds. Principal component analysis (PCA) was performed on the data of each chemical parameter to explore their usefulness for the discrimination of eleven monovarietal olive oils. Best differentiations among cultivars were obtained with triacyglycerol and sterolic compositions. The spatial distribution of the different oil samples using all the collected data showed a good discrimination among olive cultivars. A strong resolution between the samples according to the geographical origin was obtained by means of factorial discriminant analysis (FDA) (λ = 0.002). Comparisons of the distances between classes were statistically significant (Fisher tests; P < 0.0001), and 90.91% of cross‐validated grouped cases are correctly classified. The obtained results could become an important tool for sorting out oils to a single cultivar or to a specific geographical area.     

Surface tension of fatty acids and triglycerides

Surface tension as a function of temperature was measured for four fatty acids (lauric, myristic, palmitic, and oleic) and two triglycerides (tricaprylin and tripalmitin). These surface tension measurements were performed using a K12 vers. 3.1 (Krüss GmbH) tensiometer at temperatures from 20 (or the melting point of each substance) to 90°C. The constants for a van der Waals-type correlation as well as for a linear equation are presented. Both equations are quite accurate, presenting mean deviations not exceeding 0.570%. Such correlation constants are valuable in the design or evaluation of processing equipment, especially that involving gas-liquid contact such as distillation and stripping columns, deodorizers, reactors, and equipment for physical refining.     

Hydrolysis of palm oil catalyzed by macroporous cation-exchanged resin

Hydrolysis of palm oil was studied using four types of commercial H⁺-exchanged resin with acidity in the region of 5×10⁻³ eq g⁻¹ but with different pore volumes, specific surface areas, and pore diameters. The reaction was carried out in a stirred batch reactor in the liquid phase with continuous steam injection for up to 14 h. The rate of hydrolysis did not depend on total pore volume and specific surface area but did depend on pore diameter. On exchanging H⁺ with La³⁺, Co²⁺, and Na⁺, the rate of reaction decreased markedly and was dependent on the degree of exchange, demonstrating that hydrolysis was catalyzed by H⁺ sites. The activation energy for the hydrolysis of the triglycerides was estimated to be 240 kJ mol⁻¹. A procedure to estimate the rates of the different stages of hydrolysis and hence the individual rate constants of the forward and reverse reactions is described. The procedure yielded reasonable parameters for the reaction at 155°C up to 6 h of reaction time, when about 75 mol% of triglycerides was hydrolyzed.     

Carica papaya latex-catalyzed synthesis of structured triacylglycerols

One impediment to the industrial use of enzymes in fat and oil transformations is the higher cost often associated with an enzymatic process compared with the corresponding chemical process. Processes that utilize plant enzymes, however, may have advantages because of their lower cost and ready availability. One example of such a plant-derived enzyme is Carica papaya latex (CPL), the principal source of the protease papain. Recently, it has been shown that this latex also catalyzes the lipolysis of triacylglycerols and that this latex lipase has a selectivity for short-chain acyl groups as well as a 1,3-glycerol selectivity. These selectivities can be used in the synthesis of structured triacylglycerols. In this paper we describe the utility of CPL in lipase-catalyzed reactions, specifically the synthesis of low-calorie triacylglycerol analogs. Presented in part at the American Oil Chemists’ Society’s 88th Annual Meeting & Expo, Seattle, WA, May 1997.     

Effect of interesterification on the structure and physical properties of high-stearic acid soybean oils

Triglyceride structures of genetically modified soybean oils high in stearic acid were determined by high-pressure liquid chromatography, and their physical properties were assessed by dilatometry and dropping point. In their natural state, these oils lack sufficient solids at 10–33°C to qualify as margarine oils. However, after random interesterification, soybean oil containing 17% stearic acid shows a solid fat index (SFI) profile and dropping point closely matching those of a liquid margarine oil. Other oils, with stearic acid contents in the range of 20–33%, showed appreciable SFI values at 10°C but lacked sufficient solids at 21.1–33.3°C. After random interesterification, these oils also exhibited SFI profiles suitable for soft tub margarine, and their drop points increased from 18–19°C to 36–38°C.     

Triglyceride composition of ewe,cow, and goat milk fat

The separation and identification of the components in milk fat, which are mainly triglycerides, is a challenge due to its complex composition. A reverse-phase high-performance liquid chromatography (HPLC) method with gradient elution and light-scattering detection is described in this paper for the triglyceride analysis in ewes’ milk fat. Triglyceride identification was carried out by combining HPLC, gas-liquid chromatography (GLC), and the calculated equivalent carbon numbers of several triglyceride standards. Quantitation of partially resolved peaks in the HPLC chromatogram was accomplished by applying a peak deconvolution program. Forty-four fatty acids were identified by GLC analysis, but only 19 were used for the following prediction of triglyceride molecular species; 181 triglycerides were identified, some of which were grouped at the same peak and needed application of the deconvolution program. Consequently, coefficients of variation were close to or lower than 5%. Moreover, the triglyceride composition of ewe, cow, and goat milk fat were compared by using these methods. These results show that ewe milk fat is richer in short- and medium-chain triglycerides, and cow milk fat is richer in long-chain and unsaturated triglycerides.