Optimization of oligoglycerol fatty acid esters preparation catalyzed by Lipozyme 435

Esters in the Food and Cosmetic Industries: An Overview of the Reactors Used in Their Biocatalytic Synthesis

Esters are versatile compounds with a wide range of applications in various industries due to their unique properties and pleasant aromas. Conventionally, the manufacture of these compounds has relied on the chemical route. Nevertheless, this technique employs high temperatures and inorganic catalysts, resulting in undesired additional steps to purify the final product by removing solvent residues, which decreases environmental sustainability and energy efficiency. In accordance with the principles of "Green Chemistry" and the search for more environmentally friendly methods, a new alternative, the enzymatic route, has been introduced. This technique uses low temperatures and does not require the use of solvents, resulting in more environmentally friendly final products. Despite the large number of studies published on the biocatalytic synthesis of esters, little attention has been paid to the reactors used for it. Therefore, it is convenient to gather the scattered information regarding the type of reactor employed in these synthesis reactions, considering the industrial field in which the process is carried out. A comparison between the performance of the different reactor configurations will allow us to draw the appropriate conclusions regarding their suitability for each specific industrial application. This review addresses, for the first time, the above aspects, which will undoubtedly help with the correct industrial implementation of these processes.

Chemically vs Enzymatically Synthesized Polyglycerol-Based Esters: A Comparison between Their Surfactancy

Polyglycerol fatty acid esters (PGFAEs) are gaining interest in several industrial sectors due to their excellent surfactant properties and their wide range of hydrophilic-lipophilic balance (HLB) values. Moreover, they can be prepared from renewable resources, i.e., fatty acids and glycerol. In this study, polyglycerol-2 stearic acid esters (PG2SAEs) were synthesized by the enzymatic esterification of polyglycerol-2 (PG2) and stearic acid (SA) using the immobilized lipase Novozym 435 as a biocatalyst in a solvent-free system. Reaction conditions, i.e., temperature (80 °C), reactant ratio (1:1.8), and enzyme loading (2.7% w/w), were finely optimized; furthermore, biocatalyst recycling was studied by assessing the residual activity of the lipase after each reaction cycle, up to 20 times. The composition of the enzymatically synthesized products (E) was roughly evaluated by chromatographic methods and mass spectrometry and compared with that of the esters obtained by acid-catalyzed esterification (C). Then, the surfactant properties of the prepared polyglycerol-based surfactants were investigated by interfacial tension studies. Specifically, the emulsifying capacity and stability and the rheological behavior of O/W emulsions prepared in the presence of E were deeply investigated in comparison with those of the chemically synthesized and commercially available product C.

Antifungal Effect of Triglycerol Monolaurate Synthesized by Lipozyme 435-Mediated Esterification

This study was designed to synthesize triglycerol monolaurate (TGML) with Lipozyme 435 as the catalyst, and explore its effects on the growth of Aspergillus parasiticus (A. parasiticus) and Aspergillus flavus (A. flavus) and the secretion of aflatoxin b1. The highest content of TGML (49.76%) was obtained at a molar ratio of triglycerol to lauric acid of 1.08, a reaction temperature of 84.93°C, a reaction time of 6 h and an enzyme dosage of 1.32%. After purification by molecular distillation combined with the washes with ethyl acetate and water, the purity of TGML reached 98.3%. Through characterization by electrospray-ionization mass spectrometry, infrared spectrum and nuclear magnetic resonance, the structure of TGML was identified as a linear triglycerol combined with lauroyl at the end. Finally, the inhibitory effects of TGML on the growths of A. parasiticus and A. flavus and the secretion of aflatoxin b1 were evaluated by measuring the colony diameter, the inhibition rate of mycelial growth and the content of mycotoxin in the media. The results indicated that TGML had a stronger inhibitory effects on colony growth and mycelial development of both toxic molds compared to sodium benzoate and potassium sorbate, and the secretions of toxins from A. parasiticus and A. flavus were completely suppressed when adding TGML at 10 and 5 mM, respectively. Based on the above results, TGML may be used as a substitute for traditional antifungal agents in the food industry.

Green Synthesis of Decaglycerol Laurates by Lipase-Catalyzed Transesterification of Methyl Laurate with Decaglycerol

Decaglycerol laurates have been widely used as emulsifiers in food, medicine, and cosmetic industries for many years. Currently, they are synthesized using alkaline catalysts under stringent conditions. Here, decaglycerol laurates were prepared through a green lipase-catalyzed process, employing the transesterification of methyl laurate with decaglycerol by the immobilized lipase (Novozym 435). Single-factor experiments and orthogonal test were used for reaction optimization. The optimum conditions were obtained as follows: reaction temperature of 65°C, a laurate/decaglycerol molar ratio of 2 : 1, an oscillating speed of 180 rpm, an enzyme dosage (based on amount of methyl laurate) of 8 wt.%, initial water content (based on the total substrate mass) of 5.0 wt.%, and reaction time of 4.5 h with 84.4% conversion of methyl laurate. The transesterification products were identified by electrospray ionization mass spectrometer. In addition, the surface activity of decaglycerol laurates was also characterized, and the surface tension of water was reduced to 33 mN·m−1 at a concentration magnitude of 10−5 g/mL.

Enzymatic Synthesis of Polyglycerol Fatty Acid Esters and Their Application as Emulsion Stabilizers

Polyglycerol ester is considered an excellent kind of food emulsifier. The aim of the current study was to synthesize polyglycerol fatty acid esters (PGFEs) with different-sized long-chain fatty acids (i.e. long-carbon fatty acid polyglycerol esters, L-PGFEs; medium-carbon fatty acid polyglycerol esters, M-PGFEs; and short-carbon fatty acid polyglycerol esters, S-PGFEs), using Lipozyme 435 as a catalyst in a solvent-free system. Thereafter, the physicochemical properties of the newly synthesized PGFEs and their potential applications as food emulsifiers were investigated. The maximum esterification efficiencies of L-PGFEs, M-PGFEs, and S-PGFEs were 69.37, 67.34, and 71.68%, respectively, at the optimum conditions: a reaction temperature of 84.48 °C, a reaction time of 6 h, a molar ratio of polyglycerol to fatty acid of 1.35:1, and 1.41 wt % enzyme usage (based on the total substrate mass). A high-performance liquid chromatograph equipped with an evaporative light-scattering detector (HPLC-ELSD) and an electrospray-ionization mass spectrometer (ESI-MS) were employed to identify the synthesized products. The results demonstrated that the main components of these PGFEs were dimeric glycerides (68.3%), triglycerides (13.13%), and a small amount of tetraglycerides (3.18%). The properties of the PGFEs were characterized by physical and chemical methods. Compared with M-PGFEs and S-PGFEs, L-PGFEs had the best physicochemical properties without any obvious odor. Further, the emulsion capabilities of these different long-chain PGFEs were evaluated via examining the particle sizes and storage stabilities and comparing them with those of glycerin monostearate (GMS). The results showed that the emulsions prepared with L-PGFEs had the best stability and the smallest particle sizes (16.8 nm) compared with those of M-PGFEs, S-PGFEs, and GMS, and they were not prone to oil-droplet coalescence or the separation of oil and water. From the current study, the newly synthesized PGFEs with long-chain fatty acids showed the best advantages as a food emulsifier compared with M-PGFEs, S-PGFEs, and even glycerin monostearate.