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Lipase-catalyzed synthesis of secondary glucose esters under continuous flow conditions
Abstract
Chemical methods for the synthesis of sugar esters require the use of high temperatures in the presence of alkaline catalysts resulting in undesirable by-products and low regiosselectivity. Sugar-based fatty acid esters are non-ionic, biodegradable, odorless, non-irritating, non-toxic surfactants widely used pharmaceuticals, cosmetics, detergents, and food industry. Here in we report our results on enzymatic esterification of protected glucose (glucose ketal) with several fatty acids using the immobilized lipase from Rhizomucor miehei under batch and continuous flow conditions, to afford new glucose derivatives with potential surfactant properties. The results presented here shows that high conversions can be obtained in short reaction time.
Practical application: The research of new non-toxic, environmentally friendly and biodegradable surfactants to replace chemicals has increased along with the development of green chemistry. Nonionic biosurfactants, such as sugar fatty acid esters, may be obtained by enzymatic synthesis, a simple manufacturing method for application in several areas, including food, cosmetic, detergent, and pharmaceutical industry. In this work we have described the uncommon esterification of a steric hindered secondary hydroxyl group on glucose ketal leading to new glucose derivatives with potential application as surfactants.
... However, few published data are available on the synthesis of SFAEs in flow chemistry conditions. Some studies, such as by Ruela et al. [146,147], have detailed the integration of immobilized enzyme systems and continuous flow reactors for the enzymatic esterification of glucose. In their work, they used a protected glucose (glucose ketal), immobilized lipase from Rhizomucor miehei, under discontinuous and continuous flow conditions and several fatty acids. ...
Carbohydrate-based surfactants are amphiphilic compounds containing hydrophilic moieties linked to hydrophobic aglycones. More specifically, carbohydrate esters are biosourced and biocompatible surfactants derived from inexpensive renewable raw materials (sugars and fatty acids). Their unique properties allow them to be used in various areas, such as the cosmetic, food, and medicine industries. These multi-applications have created a worldwide market for biobased surfactants and consequently expectations for their production. Biobased surfactants can be obtained from various processes, such as chemical synthesis or microorganism culture and surfactant purification. In accordance with the need for more sustainable and greener processes, the synthesis of these molecules by enzymatic pathways is an opportunity. This work presents a state-of-the-art lipase action mode, with a focus on the active sites of these proteins, and then on four essential parameters for optimizing the reaction: type of lipase, reaction medium, temperature, and ratio of substrates. Finally, this review discusses the latest trends and recent developments, showing the unlimited potential for optimization of such enzymatic syntheses.
... The observed drop in the conversion for the 3rd round when the hollow microspheres were used can be explained by water sorption from the surrounding environment and ester hydrolysis (each round lasted for 6 h, set-up was not sealed and medium contained hygroscopic DMSO). Nevertheless, the investigated continuous flow system outperformed some of the previously reported SFAE continuous reactor setups [51][52][53][54][55]. ...
Hollow silica microspheres provide an ideal solid support for enzyme immobilization. We tested one of the newest development, namely MATSPHERES® a silica openwork material as a carrier for the covalent immobilization of enzymes used to synthesize bioactive compounds. Two model enzymes – ethylbenzene dehydrogenase and EL070 lipase – were considered. They belong to two different enzyme classes and catalyse reactions taking place in various environments (aqueous and non-aqueous, aerobic and anaerobic). The enzymes were immobilized by covalent bonds (via divinyl sulfone and glutaraldehyde) on new silica material. Effectiveness of immobilization processes on the spheres grafted with amine groups and on the analogues without functionalization was determined for both enzymes. Microspheres were characterized morphologically and also their mechanical stability was examined during exposure to varying physical conditions. It was shown that MATSPHERES® due to their openwork structure and relative stability under batch and flow conditions can be a competitive SBA support for enzyme immobilization and production of bioactive compounds.
... The decline might be caused by the high concentration of FFAs or the ionized carboxylic acid groups, which may acidify the lipase and cripple the activity of the enzyme. 24 In addition, the inclusion of an appropriate amount of enzyme to the reaction system allows the enzyme and substrate complex to rapidly form and exert potency. However, when enzyme is excessive, it may not be sufficiently combined with the substrate, 25 and the catalytic efficiency is lowered. ...
BACKGROUND
The silkworm pupae of Bombyx mori L. are considered to be a valuable unsaturated fatty acids (UFAs) resource. Enzymatic transesterification, which can produce structured lipids (SLs), is regarded as a desirable approach to utilize this resource, but requires long reaction time. A method to reduce the reaction time and obtain novel SLs is thus desirable. Hence, microwave irradiation was employed to reduce the reaction time and obtain novel SLs. In addition, high‐performance liquid chromatography with an evaporative light scattering detector was employed to investigate the contribution of the fatty acids (FAs) after microwave irradiation.
RESULTS
One hour was required for a 1:5 substrate ratio of silkworm pupae oil (SPO):oleic acid (OA) using a solvent‐free system catalysed by Lipozyme RM IM (7%) at 60 °C with microwave irradiation at 50 W to obtain the novel SLs. The relative content of polyunsaturated FAs glyceride increased from 51.1% to 81.0%, and the relative content of glycerol trioleate (OOO) in SPO obtained in the microwave reactor was twice as high as that in the shaker reactor. In addition, the relative content of OA was increased from 3.9% to 35.8% in total compared with the products from the shaker reactor. Furthermore, the changes of α‐helix relative content of Lipozyme RM IM were observed after the reaction under the microwave irradiation.
CONCLUSION
The results indicated that variations in the FA distribution of enzymatic transesterification reactions caused by microwave irradiation could aid the addition of OA and enrichment of UFAs. © 2019 Society of Chemical Industry
... Presumably, the high viscosity of neat DES has been a hurdle for research groups to undertake research in that area. Since viscosity can decrease significantly with addition of water as co-solvent, the created DES-water blends can serve as reactor media for continuous processes (Ruela et al., 2013). Herein, advantageous of this system is the viscosity decrease together with an efficient substrate solubility and with a high enzyme-compatibility, what may enable the implementation of the reaction on a large scale. ...
This work explores for the first time the use of Deep Eutectic Solvents (DES) with phosphate buffer 100 mM pH 7 as cosolvent (10% v/v) in biocatalytic reactions in fed-batch and packed-bed bioreactors. The lipase-catalyzed esterification of glycerol and benzoic acid is studied, as it involves two substrates with different polarities (for which DES are needed). In the fed-batch bioreactor, the highest conversion (90%) was obtained at a substrate flow rate of 0.01 mL / min. The fed-batch operation increased the conversion by 59% compared to the batch mode. Regarding productivity, semi-continuous and continuous bioreactors showed analogous results. Upon recirculation of the reaction media in the continuous bioreactor, a conversion of 67% was achieved in 7 cycles of operation. The stability of the biocatalyst in the packed-bed bioreactor decreased only 2% in 10 days, demonstrating the attractiveness that low viscous DES-water mixtures with continuous processes may have.
... In a recent study, lipase from Aspergillus ibericus has been used for the esterification reactions and aroma ester production [189]. A variety of fatty acid esters are now produced commercially by using immobilized lipase in nonaqueous solvents [190][191][192][193]. ...
Lipases (triacylglycerol hydrolases, E.C. 3.1.1.3) occupy a prominent place among biocatalysts and carry out reactions in aqueous and non-aqueous media. They catalyze both the hydrolysis and synthesis of long chain acylglycerols. The chemo-, regio- and enantio- specific characteristics of lipase tend to be a focus research area for scientists and industrialists. Compared to plants and animals, microorganisms have been found to produce high amount of lipases. Fungal lipases stand out as the major sources of the enzyme because of their catalytic activity, low cost of production and relative ease in genetic manipulation. This review describes the various sources of lipases, their properties, purification methods, immobilization techniques, and potential industrial applications that make lipases to be biocatalysts of choice for the present and future. The aim of this review is to present recent information on fungal lipases.
... Unprotected sugars are soluble only in a few hydrophilic organic solvents such as pyridine and dimethylformamide, which are, however, poor solvents for lipase activity [10]. Two strategies have been pursued to solve this problem: one strategy utilizes chemical modification on the substrate, typically the sugar, to make it more hydrophobic and hence more soluble [11][12][13][14][15]; the other strategy is based on solvent engineering. In this second strategy, ionic liquids (ILs) have shown great potential as a green alternative reaction medium to conventional organic solvents for sugar ester synthesis, promoting a significant enhancement in sugar solubility, enzymatic reactivity, and regioselectivity [7]. ...
Sugar fatty acid esters (SFAEs) are biocompatible nonionic surfactants with broad applications in food, cosmetic, and pharmaceutical industries. They can be synthesized enzymatically with many advantages over their chemical synthesis. In this study, SFAE synthesis was investigated by using two reactions: (1) transesterification of glucose with fatty acid vinyl esters and (2) esterification of methyl glucoside with fatty acids, catalyzed by Lipozyme TLIM and Novozym 435 respectively. Fourteen ionic liquids (ILs) and 14 deep eutectic solvents (DESs) were screened as solvents, and the bisolvent system composed of 1-hexyl-3-methylimidazolium trifluoromethylsulfonate ([HMIm][TfO]) and 2-methyl-2-butanol (2M2B) was the best for both reactions, yielding optimal productivities (769.6 and 397.5 µmol/h/g, respectively) which are superior to those reported in the literature. Impacts of different reaction conditions were studied for both reactions. Response surface methodology (RSM) was employed to optimize the transesterification reaction. Results also demonstrated that as co-substrate, methyl glucoside yielded higher conversions than glucose, and that conversions increased with an increase in the chain length of the fatty acid moieties. DESs were poor solvents for the above reactions presumably due to their high viscosity and high polarity.
... A variety of fatty acid esters are now being produced commercially using immobilized lipase in nonaqueous solvents [21,[113][114][115]. The esters produced from long-chain fatty acids (12-20 carbon atoms) and short-chain alcohols (three to eight carbon atoms) have been used in food, detergent, cosmetic, and pharmaceutical industries [116]. ...
The lipase of Bacillus licheniformis SCD11501 was purified with a fold purification of 10.6 and a yield of 8.4 % by ion-exchange chromatography on a DEAE-cellulose column. The purified enzyme was found to be electrophoretically pure by denaturing SDS-PAGE and possessed a Mr of approximately 35 kDa. A single band ~70 kDa was observed in native-PAGE confirming that the lipase of B. licheniformis appeared to be a holozyme that comprises two identical subunits of ~35 kDa in SDS-PAGE. Thus the lipase appeared to be a homodimeric protein which was an interesting observation. The purified lipase was optimally active at 55 °C and pH 9.5 and showed maximum hydrolytic activity towards a relatively longer C-chain length p-NPP substrate. The lipase was stimulated only in the presence of Fe2+ while the presence of the chelating agent(s) inhibited its activity. All surfactants (Triton X-100, Tween 20, Tween 40, Tween 60, Tween 80 and SDS) had an inhibitory effect on lipase activity. The purified lipase also retained good activity in the presence of both hydrophobic (n-hexane) as well as hydrophilic (DMSO) solvents that indicated its usefulness in promoting both hydrolytic as well as synthetic reactions. The extracellular lipase was highly thermostable as it showed a half-life of 150 min at 55 °C and 60 min at 75 °C. The K
m
and V
max of purified lipase of B. licheniformis SCD11501 was found to be 0.43 mM and 2.27 µmol/ml/min, respectively for hydrolysis of p-NPP.
... This allowed obtaining phospholipid fractions containing up to 80% DHA. The optimization of biocatalytic continuous flow processes was discussed by R. de Souza (Rio de Janeiro, BR), comparing various lipase-catalyzed reactions in packed-bed and batch reactors to underline the importance of optimization methods in biocatalyzed process development [2]. ...
This three day event was organized by Uwe Bornscheuer and Pierre Villeneuve (division of biotechnology and enzyme technology of Euro Fed Lipid) in cooperation with SFEL (Société française pour l'étude des lipides) and the DGF (Deutsche Gesellschaft für Fettwissenschaft e.V.). The meeting was held at the Institute of Biochemistry of the Greifswald University, Greifswald – a small town at the Baltic coast of Mecklenburg-Vorpommern in northeastern Germany. About 60 scientists discussed recent developments in basic research and industrial process development involving enzymatic lipid modification. EJLST will publish a special issue based on the Greifswald meeting in late spring/early summer 2013; this meeting report will give you a flavor of what will be covered.
... A variety of fatty acid esters are now being produced commercially using immobilized lipase in nonaqueous solvents [21,[113][114][115]. The esters produced from long-chain fatty acids (12-20 carbon atoms) and short-chain alcohols (three to eight carbon atoms) have been used in food, detergent, cosmetic, and pharmaceutical industries [116]. ...
Lipases are a group of enzymes naturally endowed with the property of performing reactions in aqueous as well as organic solvents. The esterification reactions using lipase(s) could be performed in water-restricted organic media as organic solvent(s) not only improve(s) the solubility of substrate and reactant in reaction mixture but also permit(s) the reaction in the reverse direction, and often it is easy to recover the product in organic phase in two-phase equilibrium systems. The use of organic solvent tolerant lipase in organic media has exhibited many advantages: increased activity and stability, regiospecificity and stereoselectivity, higher solubility of substrate, ease of products recovery, and ability to shift the reaction equilibrium toward synthetic direction. Therefore the search for organic solvent tolerant enzymes has been an extensive area of research. A variety of fatty acid esters are now being produced commercially using immobilized lipase in nonaqueous solvents. This review describes the organic tolerance and industrial application of lipases. The main emphasis is to study the nature of organic solvent tolerant lipases. Also, the potential industrial applications that make lipases the biocatalysts of choice for the present and future have been presented.
Besides plants and animals, the Fungi kingdom describes several species characterized by various forms and applications. They can be found in all habitats and play an essential role in the excellent functioning of the ecosystem, for example, as decomposers of plant material for the cycling of carbon and nutrients or as symbionts of plants. Furthermore, fungi have been used in many sectors for centuries, from producing food, beverages, and medications. Recently, they have gained significant recognition for protecting the environment, agriculture, and several industrial applications. The current article intends to review the beneficial roles of fungi used for a vast range of applications, such as the production of several enzymes and pigments, applications regarding food and pharmaceutical industries, the environment, and research domains, as well as the negative impacts of fungi (secondary metabolites production, etiological agents of diseases in plants, animals, and humans, as well as deteriogenic agents).
Acetimidates, a valuable intermediate has been well explored as versatile synthon in a number of organic transformations particularly as suitable donors in glycosylation reactions. Herein, we explored acetimidates to furnish high-to-excellent yield of diverse glycosylated esters under one-pot mild reaction condition. The commercially available trichloroacetonitrile is implemented for the activation of carboxylic acid via in situ generation of trichloroacetimidate, which was subsequently attacked by sugar alcohols to deliver high-to-excellent yields of desired glycosylated esters. The devised method has some notable features such as metal-free condition, one-pot mild reaction condition, easy-handling, high-to-excellent yields, and broad substrate scope.
Diacylglycerols (DAG) have been widely used in many industries due to their remarkable capabilities as emulsifiers and stabilisers. However, developing a sustainable and an effective synthesis method for DAG remains a challenge. Continuous flow bio-reactor is recognized to be more productive, controllable, and reliable instrument for developing green and intensified processes. In this work, a continuous flow packed bed millireactor was employed for the synthesis of glycerol dioelate (GDO) catalyzed by immobilized lipase namely Candida antartica. Experiments were carried out to evaluate the kinetic parameters as well as to assess the internal and external mass transfer limitations. Using one-factor-at-a-time variables method, maximum oleic acid conversion and GDO selectivity were achieved at 85% and 74% respectively, at 0.15 g of lipase, 77 min of residence time with 1.6:1 molar ratio of oleic acid/glycerol. Hydrodynamic studies showed that the esterification reaction is kinetically controlled and unaffected by external and internal mass transfer. Employing Lilly–Hornby model for kinetic evaluation, Km values increased with increasing flow rates, whereas, Vmax appeared to be flow rate independent. Reusability tests revealed that the activity of immobilized lipase remained the same after 9 successive reaction cycles. At 11 days of operation, the stability of the lipase in the continuous packed bed millireactor decreased only 5–7%, indicating satisfying operational results and recyclability. This work may promote the enzymatic engineering synthesis of DAG, facilitating the creation of a cleaner and safer process. It has the potential to broaden the application of enzymes in continuous flow micro or millireactors.
This paper describes the regioselective production of palm‐based sorbitol monoesters via esterification catalyzed by Lipozyme® TL IM (Thermomyces lanuginosus lipase adsorbed onto silica gel, Novozymes, Inc., Franklington, NC, USA). Effects of various reaction parameters including types of solvent, substrate molar ratio, molecular sieve and lipase concentration, temperature, reaction time, and fatty acid chain length were investigated. Approximately 76% conversion of sorbitol to sorbitol esters was achieved within 24 h under optimal conditions: sorbitol (0.4 M), fatty acid (0.8 M), 20 wt% Lipozyme® TL IM in 100 mL tert‐butanol at 55 °C for 24 h in the presence of 25 wt% 3 Å molecular sieve as water absorbent. The reactions were conducted in an orbital incubator shaker at a shaking rate of 200 rpm. Lipozyme® TL IM was highly regioselective, esterifying exclusively at sorbitol's primary hydroxyl groups, producing 1‐O‐ and 6‐O‐sorbitol monoesters. The biocatalyst also exhibited substrate selectivity toward shorter chain acyl donors, with caprylic acid exhibiting the highest conversion of sorbitol. In addition, Lipozyme® TL IM was reused up to four successive reaction cycles without significant loss of activity. The biocatalytic process reported in this paper is a one‐step process to produce biobased surfactants that does not involve the use of toxic or expensive solvents that are commonly employed for derivatization of sugars, or pre‐derivatization of the substrates molecules.
In the past few decades, organic reactions under flow conditions have attracted increasing attention. Flow reactions have a number of advantages over batch reactions in terms of environmental compatibility, efficiency, and safety. In particular, flow reactions with heterogeneous catalysts that yield desired products without significant levels of by-product formation can enable purification processes to be avoided. This feature can allow flow reactions to be assembled in a multi-step and continuous manner for the synthesis of complex molecules. These new techniques have opened up new approaches to the synthesis of fine chemicals and are expected to play a prominent role in future chemical manufacturing processes. In this context, this review aims to summarize recent developments in continuous-flow reactions with heterogeneous catalysts for synthesis of fine chemicals.
Enzymes are useful catalysts in the environmentally friendly production of chemical substances with applications in everyday life. Nevertheless, problematic features such as the stability of the enzymes, the cost, and efficiency of the reactions lead to rather limited industrial usage. Thus, continuous flow processing has been considered as a possible tool to solve some of the challenging aspects of enzymatic synthesis.
New challenges have to be faced in the field of surfactants. Green processes and products are increasingly demanded: green syntheses, natural building blocks as starting materials, products of high biodegradability and devoid of toxicity, low costs. Sugar-based surfactants successfully fit all these requirements and thus they are at the centre of the research of new green surfactants with specific properties. Most of the syntheses published in the literature from 2008 to 2014 are about new structures presenting variations on the sugar moiety, the hydrophobic chain, and the introduction of spacer arms between the polar head and the lipophilic tail. Carbohydrates offer a wide diversity of monomers and dimers that can be cyclic (furanose, pyranose) or acyclic to be used as a polar head. Among all the available hydroxyl groups of a sugar unit, two are particularly suitable for substitution: primary alcohols and the hydroxyl at the anomeric position. The hydrophobic chain can be more complex than the classical alkyl chain, as chemists are looking for new properties that can be brought by the use of fluoroalkyl chains or polysiloxanes. This chapter reviews recent bibliography and reports (patents excluded) on the synthesis of sugar-based surfactants, including chemical and chemoenzymatic methods.
Objective: The objective of this study was to investigate the susceptibility of five Food pathogenic or spoilage bacteria strains to the antimicrobial properties of fatty acid fructose esters.
Packed bed reactors can be used as an interesting alternative on the bioreduction of β-ketoesteres mediated by immobilized microorganisms. Here in, we report our results on the bioreduction of ethyl 3-oxohexanoate by immobilized Kluyveromyces marxianus cells and tert-butyl 3-oxobutanoate by immobilized Rhodotorula rubra cells under continuous flow conditions leading the desired β-hydroxy esters corresponding in high yields and enantiomeric excess.
Sugar-based organogels are important esters for the cosmetic, food and pharmaceutical industries due to their intrinsic properties. Chemical routes to obtain these molecules suffer from low yields and undesirable side products. In this way, biocatalysis can be an interesting and efficient alternative, which meets the green chemistry principles. Herein we report our results on the development of a continuous flow process for the production of sugar-based surfactants mediated by immobilized enzymes in microemulsion based organogels, leading to the desired product in high productivities (66.8 to 88.1 g of ester per h per g of lipase).
Desilked silkworm ( Bombyx mori L .) pupae oil has been identified as a valuable source of unsaturated fatty acids (UFAs). However, direct consumption is a food safety issue due to the presence of sn ‐1,3 triacylglycerols (TAGs), including palmitic acid (PA). A simple, selective and safe conversion to structured triacylglycerols (STAGs) with high UFA content is highly desirable. Novel STAGs with low PA and high α ‐linolenic acid (ALA), oleic acid (OA) and linoleic acid (LA) content were synthesized from silkworm pupae oil using a solvent‐free system catalyzed by Lipozyme RM IM. Crystallization and melting profiles were determined using thermograms, and optimal conditions involved an enzyme load of 7%, a silkworm pupae oil TAG to OA molar ratio of 1:5, and a reaction temperature of 60°C. The content of PA and stearic acid decreased from 41.04 to 20.11%, while UFAs increased from 61.12 to 77.88%. The STAGs exhibited lower crystallization (−15.44°C) and melting (−23.47°C) profiles than TAGs (4.64 and −5.58°C, respectively).
Practical applications
The presented methods using a solvent‐free system enable STAGs to be synthesized using a natural substrate (desilked silkworm pupae oil). A simple, selective and safe conversion to STAGs with high UFA content and low PA content is highly desirable. This STAG is rare in nature and chemical synthesis is cumbersome. This STAG could be applied as a clinical treatment for nutritional enhancement with a beneficial effect on human health because of the high content of the ALA.
Novel structure triacylglycerols (STAGs) with low palmitic acid and rich in oleic acid and linoleic acid were synthesized from silkworm pupae oil and oleic acid, through solvent‐free enzymatic interesterification catalyzed by Lipozyme RM IM. Under the optimal conditions, the content of palmitic acid and stearic acid decreased from 41.04 to 20.11% in the sn‐1, 3 positions, and the content of unsaturated fatty acids (including palm stearin, oleic acid, linoleic acid and α‐linolenic acid) increased from 61.12 to 77.88%. The STAGs could be added into milk fat substitutes, which may be useful as nutrition enhancers for infants and may decrease obesity.
Alkyl derivatives of glucose, galactose and fructose were acylated by lipase-catalyzed transesterification with alkanoic esters. The best results were obtained with immobilized lipases of the Candida antarctica type. Primary alcohol functions were acylated first; followed by secondary ones depending on the structure of the glycoside. The water activity in the reaction medium had a striking effect on both the rate and the selectivity of the process. The size and orientation of the alkyl substituent and the structure of the acyl acceptor were also found to exert a profound influence on the course of the reaction.
Enzyme immobilisation technology is an effective means to improve sugar ester production through the employment of biocatalysts. In the present study, immobilisation of Candida rugosa (CRL) lipase onto amino-activated mica is performed via covalent bonding (namely Amino-CRL) and the cross-linking of lipases into nano-reactors through physical adsorption (namely NER-CRL). Free and immobilised lipases were tested for their esterification activities. Specific activities for Amino-CRL and NER-CRL increased by 2.4 and 2.6-fold, respectively, upon immobilisation. Extending this work, immobilised lipases have novel capabilities in the synthesis of sugar esters. The optimised conditions for sugar fatty acid ester syntheses are 48 h at 2:1 of molar ratio of lactose sugar to capric acid at 55 °C. Furthermore, a high operational stability with half-lives of over 13 and 10 runs was achieved for NER-CRL and Amino-CRL, respectively, indicating the efficiency of the immobilisation process.
Sugar esters are compounds with surfactant properties (biosurfactants), i.e., capable of reducing the surface tension and promote the emulsification of immiscible liquids. On the other hand, as with all emulsions, coconut milk is not physically stable and is prone to phase separation. Therefore, the aim of this work was to evaluate the synthesis of fructose, sucrose and lactose esters from the corresponding sugars using Candida antarctica type B lipase immobilized in two different supports, namely acrylic resin and chitosan, and evaluate its application in the stabilization of coconut milk emulsions. The enzyme immobilized on chitosan showed the highest yield of lactose ester production (84.1%). Additionally, the production of fructose ester was found to be higher for the enzyme immobilized on the acrylic resin support (74.3%) as compared with the one immobilized on chitosan (70.1%). The same trend was observed for the sucrose ester, although with lower percentage yields. Sugar esters were then added to samples of fresh coconut milk and characterized according to their surface tension, emulsification index and particle size distribution. Although the microscopic analysis showed similar results for all sugar esters, results indicated lactose ester as the best biosurfactant, with a surface tension of 38.0 N/m and an emulsification index of 54.1%, when used in a ratio of 1:10 (biosurfactant:coconut milk, v/v) for 48 h experiments.
Sugar-based surfactants, such as sorbitan esters, sucrose esters, alkyl polyglycosides, and fatty acid glucamides gain increasing attention due to advantages with regard to performance, health of consumers, and environmental compatibility compared to some standard products. Sorbitan esters are well established products, which are mainly used as leather and textile auxiliaries or as emulsifiers for food at a volume of approx. 20,000 t/a. Sucrose esters are relatively hydrophobic products. The actual market size is estimated to be < 4,000 t/a - the main application being emulsifiers for food and cosmetics. Their use is still limited. Alkyl polyglycosides and fatty acid glucamides represent a perfect amphiphilic structure with excellent surface activity as well as solubility due to highly selective syntheses. For alkyl polyglycosides industrial processes have been developed in the past couple of years and a total capacity of ca. 80,000 t/a has been established. They are mainly used for cosmetic, manual dishwashing, and detergent applications. Fatty acid glucamides to date are exclusively used by one company in liquid and powdered detergents. The estimated production capacity is approx. 40,000 t/a. Comparable in their performance profile as co-surfactants, both products differ in their raw material base: whereas in the case of the fatty acid glucamides methylamine is incorporated in the product, alkyl polyglycosides are completely based on renewable resources. This, combined with very good performance and mildness, could be one reason why alkyl polyglycosides are the most successful sugar-based surfactants nowadays. Research to develop derivatives on this basis is still ongoing.
The resolution of α- and β-anomers of glucopyranosides and galactopyranosides was achieved via enzyme-catalysed regioselective acylation. This two-step procedure to prepare pure α- and β-anomers of glycopyranosides would be most useful for the cases where glycosidases are not available or expensive to purchase. From a synthetic viewpoint, the regioselective acylation of glycopyranosides provides access to mono- and di-esters with well-defined substitution patterns.
In this review, a comprehensive and illustrative survey is made of the regioselective synthesis of esters of sugars and related compounds using lipases. The main emphasis has been given to the screening and use of commercially available lipases for the enzymatic esterification of neutral monosaccharides, disaccharides, sugar alcohols and their selected ether and ester derivatives. The effect of solvents and solubilizing agents in improving the yields of the resultant sugar fatty acid esters has been incorporated. Further, solvent‐free esterification with molten fatty acids, use of ionic liquids and microwave radiations for improvement in the methodology have also been discussed. Copyright © 2006 Society of Chemical Industry
The acylation of glucose with lauric acid in a reaction catalysed by two Candida lipases and a Mucor miehei lipase in supercritical carbon dioxide (SCCO2) was investigated. A linear dependence of the reaction rate on enzyme concentration was observed. Studies on the effect of temperature on enzyme activity showed that Candida antarctica lipase remains stable at temperatures as high as 70°C. Non-immobilised Candida rugosa lipase was found to have a temperature optimum at 60°C. The acylation reaction rate depended on the initial water activity of both substrates and enzyme; the optimum was 0·75 for Candida antarctica lipase, 0·53 for Candida rugosa lipase, and between 0·3 and 0·5 for Mucor miehei lipase. Candida rugosa lipase was most active at a molar ratio of sugar: acyl donor of 1: 3, while the optimum ratio was found to increase to 1: 6 when the reaction was catalysed by Candida antarctica and Mucor miehei lipases. © 1998 SCI
Free fatty acids are used in many cases for the production of soaps, candles and assist processing of rubber products, but we believe that new process technology should be developed to produce products with higher added value. Monoacylglycerols (MAGs) are nonionic surfactant, highly hydrophobic and has been used as controlled release systems for drugs. The results presented here for the lipase-catalyzed MAG production show that both batch and continuous flow conditions can lead to the desired product in short reaction time and high yield (70–95%) but the use of packed bed reactors (PBR) shows higher efficiency when compared to batch reactors.
The lipase catalyzed sugar ester synthesis is an interesting strategy for producing biodegradable, non-ionic surfactants. The main disadvantage of this protocol is the long reaction time required for achieving moderated to good yields. Here, we report the esterification of steric hindered fructose derivative where important variables for batch conditions were identified by the use of a RSM protocol and then translated to the continuous flow regime with high conversions and short residence times.
Diacylglycerols (DAG) are commonly used in different purity levels for food, medicine and cosmetic industries. Several approaches are found over the literature on DAG production under lipase-catalyzed reactions among which are highlighted: glycerol sterification, vegetable oils’ glycerolysis and selective hydrolysis. Results obtained palm oil partial hydrolysis catalyzed by PS Amano IM under microwave irradiation show that DAG can be produced through short-term reactions and moderated yields (5min, 30%). The DAG production using packed bed reactors under conventional heating and continuous flow conditions is more efficient allowing us to produce 128g in 24h with flow rate as a key feature.
Biodegradable, biocompatible and nontoxic nonionic surfactants are widely used in food, pharmaceutical and
industrial applications being commonly produced based on alkaline-catalyzed chemical glycerolysis of natural oil and fats at high
temperatures and elevated pressure under nitrogen atmosphere. In this work we have optimized a biocatalytic continuous flow process with packed bed reactor for the esterification reaction between (R,S)-1,2-isopropylidene glycerol and stearic acid using response surface methodology (RSM) leading to the desired product in excellent conversion (95%) and short reaction time (40 s of residence time).
Role of biosurfactants has shown renewed interest; hence, search for readily available natural resources of these materials is continuing. Chicken viscera and bahera oil were used as natural sources of oleic acid and its methyl ester, respectively, for the preparation of biosurfactants. Enzymatic esterification and transesterification of oleic acid were performed with sorbitol, fructose and ascorbic acid using Candida antarctica lipase, and their isolated yields were compared. Oleyl esters of sorbitol, fructose and ascorbic acid were produced 27, 21 and 12%, respectively. Transesterification reaction gave better yield than esterification reaction. Synthesized products were confirmed by nuclear magnetic resonance spectroscopy. Radical scavenging activity of synthesized ascorbyl oleate was compared with ascorbic acid using 1,1-diphenyl-2-picryl hydrazyl radical. Ascorbyl oleate showed better antioxidant activity than ascorbic acid.
Fatty acid esters of polyols have important applications because of their surface-active properties resulting from the combination of hydrophilic and hydrophobic parts in a single molecule. These compounds are widely used as surfactants in the food, detergent, pharmaceutical and cosmetic industries. Ascorbyl ester can be used as biosurfactant as well as fat-soluble antioxidant for prevention of oxidation of fat used in foods.
Purified lipases (via interfacial activation on hydrophobic supports) from different microbial extracts have been evaluated in the regio-selective hydrolysis of peracetylated sugars (peracetylated glucose, ribose and sucrose). Among the enzymes tested, lipases from Candida rugosa (CRL) and from Pseudomonas fluorescens (PFL) exhibited the best properties in these reactions.Then, we have prepared two different immobilized lipase preparations obtained by interfacial activation on hydrophobic supports or by covalent attachment on glutaraldehyde agarose. Interfacially activated lipases exhibited a higher activity than covalently attached enzymes (even by a 100-fold factor), giving the higher yields of mono deacetylated sugars (in some instances by more than a threefold factor) in short reaction times. In the hydrolysis of 1,2,3,5-tetra-O-acetyl-β-d-ribofuranose catalyzed by PFL adsorbed on octyl agarosa, hydrolyzed mainly the 3 position (30% of yield) while the CRL gave the hydrolysis only in position 5 (about 50% of yield).Depending on the enzyme immobilized preparation, we have been able also to obtain selective hydrolysis of 1,2,3,4,6-penta-O-acetyl-α/β-d-glucopyranose obtaining a free hydroxyl group in position 1, 4 or 6. Moreover, selective hydrolysis in the 4′ position of peracetylated sucrose was achieved when the hydrolysis is performed with CRL immobilized on octyl-agarose (yield was 77%).
A simple kinetic model derived from a Ping–Pong mechanism is proposed to describe the mono-esterification of glucose with stearic acid catalyzed by immobilized lipases from Candida sp. The mathematical expressions derived from this model have been tested with several sets of data obtained from reactions carried out at the different reactive temperatures. The predicted values provide very good fits of the experimental data for reactive temperatures from 35 to 45 °C, and the rate constants of the corresponding mechanistic reaction are obtained. The activation energy 19.4 kJ/mol is estimated for the formation of the monoester. The model also considers the kinetics of inactivation of the immobilized Candida sp. during the reaction. Reactive condition with 0.8 g molecular sieves/2 mL acetone at 35 or 40 °C for 48 h is good for the enzyme to keep its activity and for making the equilibrium produce glucose monoester of stearic acid.
Two immobilized lipases fromCandida antarctica (SP 382) andC. cylindraceae, nowrugosa (2001), catalyzed the synthesis of novel acetylated glucose fatty acid esters with glucose pentaacetate (GP) and Trisun 80
(80% oleic) vegetable oil or methyl oleate as substrates in organic solvents. The relative yield was between 6.4–52%, and
the incorporation of oleic acid onto the glucose was between 31–100%. In addition, these enzymes were able to catalyze the
synthesis of glucose fatty acid esters with free glucose as the sugar substrate. The highest oleic acid incorporation (100%)
was obtained in benzene with SP 382 lipase and Trisun 80 as the acyl donor. With methyl oleate as the acyl donor, greater
incorporation was obtained in benzene (90.5%) compared to 75% in isooctane. The 2001 lipase was better in benzene/pyridine
(2∶1 vol/vol) 74%) and chloroform (61%) compared to benzene and isooctane. However, with free glucose and Trisun 80 as substrates,
both enzymes gave acceptable levels of oleic acid incorporation (82–100%) in benzene, benzene/pyridine and pyridine. The best
conditions for the ester interchange reaction reported are: lipase (10% by weight of substrate); incubation time 48 h; molar
ratio of Trisun/GP 1∶2; 3 mL solvent and 3% added water. These glucose esters have potential applications as emulsifiers in
food, cosmetics and pharmaceutical formulations.
The present paper provides a general overview of the factors involved in both the kinetics and the selectivity of partial acylation reactions of polyols (sugars). Different kinetic strategies for maximum production of intermediate esters of various polyols and monosaccharides are reported and discussed. Physicochemical requirements for obtaining maximum selectivities and complementary strategies for reducing reaction times are discussed. The reactions studied include glycerol, glucose, fructose, mannose, sorbitol and an alkyl glucoside as precursors. The high selectivity towards the monoglyceride in the presence and absence of a solvent has been attributed to a combination of the precipitation of the desired ester, use of glycerol in excess and the relatively low solubility of the fatty acid in the system. Unlike the reaction in the presence of a solvent, the reaction in a solvent-free medium produces the diester first. The monoester only accumulates in the medium as a consequence of disproportionation and glycerolysis reactions of the diester formed earlier. Selective esterification of solid sugars (polyols) which have an intermediate solubility in acetone is favored at low temperatures at which a sufficient amount of polyol dissolves and concurrent precipitation of the desired product can be achieved. By contrast, use of elevated temperatures is more appropriate for selective partial esterification of polyols, which are the most soluble in the solvent employed. Polyols (sugars) which are the less soluble into the liquid reaction phase cannot be easily esterified. Diffusional limitations on the rate of dissolution of the solid precursor can be minimized by increasing the surface area of the solid polyol.
Abstract Various fatty monoesters of sugars and sugar alcohols were prepared enzymatically in organic solvent. Water produced during esterification was removed by refluxing through a dessicant under reduced pressure. Surface properties of these esters such as surface and interfacial tensions and their ability to stabilize emulsions at 30C were evaluated: oleate esters of glucose, fructose, and sorbitol show similar behavior in reduction of surface and interfacial tensions, and values for the critical micelle concentration are about 810−5 M. It was also observed with sorbitol esters that the shorter the alkyl chain, the higher the critical micelle concentration. Generally, emulsions prepared with the emulsifier dissolved in the water or in the oil phase lead to oil-in-water or water-in-oil emulsions, respectively. Sorbitol monolaurate significantly increased the stability of oil-in-water emulsions, with only 5% separation of the phases after 48h at 30C, compared to 10% for chemically prepared sorbitan monolaurate under the same conditions. Sorbitol monoerucate was very efficient in stabilizing water-in-oil emulsions, with only 1% separation of the phases.
In 1964, a method was described for the determination of free fatty acids (FFAs) in vegetable oil. This paper describes an
expansion of that work, improving the sensitivity and reproducibility of the method, as well as examination of solubilities
of the copper soaps as a function of chain length and unsaturation. Involvement of the micellar structure was reviewed. Finally,
a procedure is described that permits very rapid determination of FFA at the 2.0–14.0 µmol (0.5–4.0 mg oleic acid) level,
and the results with several oils are given. Particular attention was given to evaluation of solvent systems which would extract
the copper complexes.
To establish the utility of lipase as a biocatalyst, the effects of glucose on the hydrolysis activities of lipase were investigated. Among 13 kinds of lipase from microorganisms, 6 lipases were inhibited in hydrolysis up to 50% of the original activities by 10 mM glucose. The activities of other microbial lipases and 2 kind of porcine pancreatic lipases were not affected by the addition of glucose. Six lipases that were sensitive to glucose were modified by a synthetic detergent. After they were converted to modified lipases, they were not inhibited by glucose. Even at 20 mM glucose, each modified lipase retained more than 95% activity compared with that in the absence of glucose. In the modified lipase, the detergent attached to the lipase molecule would disturb the access of glucose to the enzyme. To detect the interaction between lipase and glucose, the fluorescence of tryptophan was traced. The fluorescence intensities of lipases that were inhibited by glucose depended on the concentration of glucose, suggesting that glucose induced some structural change in the lipase molecule.
The acylation of the rare sugar, D-allose (the C-3 epimer of D-glucose), with fatty acid vinyl esters was successfully carried out using Candida antarctica lipase in acetonitrile at 45 degrees C to give D-allose 6-alkanoates with high regioselectivity in good yields.
The transesterification of D-allose (the C-3 epimer of D-glucose) with vinyl octanoate using Candida antarctica lipase in tetrahydrofuran proceeded with high regioselectivity to produce 6-O-octanoyl-D-allose with nearly complete conversion. The growth-inhibiting activity of 6-O-octanoyl-D-allose on lettuce seedlings was about 6-fold greater than that of D-allose.
Acylation of glucose catalysed by lipases in supercritical carbon dioxide
- Tsitsimpikou