Enzymatic synthesis of 6- and 6′-O-linoleyl-α-d-maltose: From solvent-free to binary ionic liquid reaction media

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Enzymatic synthesis of amphiphilic carbohydrate esters: Influence of physicochemical and biochemical parameters

Glycolipids, carbohydrate fatty esters or sugar esters are amphiphilic molecules containing hydrophilic groups bonded to hydrophobic parent structures. Recently, glycolipids have shown their antimicrobial and antitumor capacities. Their surface activity properties have applications in the food, pharmaceutical and cosmetic industries. Sugar esters' building blocks can be obtained from natural resources and/or be transformed by biochemical pathways for uses as surfactants. Biosurfactants are non-ionic, nontoxic, biodegradable, tasteless, and odourless. The biocatalysis of these molecules involves sustainable, green, and safer methods. The advantages of producing biosurfactants from enzymatic catalysis are the energy economy, high selectivity, production of natural products, reduction of the use of fossil-based solvents and chloride compounds. This review presents the most recent studies concerning the evaluation of the impact of the main parameters and their levels influencing the enzymatic synthesis of glycolipids. Various enzyme catalysed synthetic methods were described. The parameters studied were temperature, reaction time, solvent system, type of biocatalyst, substrates molar ratio proportion and the nature of substrates. This review discusses the influence of different biocatalysts in the conversions of glycolipids; The reactivity from mono to polysaccharides and their interaction with fatty acids of different carbon chain lengths in the presence of specific enzymes; The effect of the solvent polarity, the use of multiple solvents, ionic liquids, supercritical CO₂, and solvent-free media in sugar ester conversions; And the optimization of temperature and reaction time in different enzymatic systems.

Regioselective Dehydration of Sugar Thioacetals under Mild Conditions

Sugars are abundant in waste biomass, making them sustainable chiral building blocks for organic synthesis. The demand for chiral saturated heterocyclic rings for pharmaceutical applications is increasing as they provide well-defined three-dimensional frameworks that show increased metabolic resistance. A range of sugar thioacetals can be dehydrated selectively at C-2 under mild basic conditions, and the resulting ketene thioacetals can be applied to the production of useful chiral building blocks via further selective dehydration reactions.

Reviewing research on the synthesis of CALB-catalyzed sugar esters incorporating systematic mapping principles

Rigorous evidence reviews must follow specific guidelines designed to improve transparency, reproducibility, and to minimize biases to which traditional reviews are susceptible. While evidence synthesis methods, such as systematic reviews and maps, have been used in several research fields, the majority of reviews published in the realm of chemical engineering are nonsystematic. In this study, we incorporated principles of systematic mapping to conduct a literature review covering research on the synthesis of sugar fatty acid esters (SFAE) with Candida antarctica lipase B (CALB). Our results showed that the simple monosaccharides were the most cited sugars among studies we conducted. The direct use of renewable raw materials and frequently available resources to produce alternative sugar esters (SE) was scarcely reported in our data set. We found that free fatty acids (FFA) were the most commonly cited acyl donors amongst all publications, with lauric, oleic, and palmitic acids accounting for ∼43% of the occurrences. Tertiary alcohols (ter-butyl alcohol (T-but) and 2-methyl-2-butanol (2M2B)) and ionic liquids were the most used solvents to synthesize SE. The co-occurence analysis of keywords involving solvent terms showed that most of the papers evaluated different solvents as reaction media (mostly in the form of a bisolvent system), also investigating the impact of their choice on sugar ester productivities. Given the potential of reviews informing us of research decisions, this article reveals trends and spaces across CALB-catalyzed SE synthesis research, in addition to introducing a new methodological perspective for developing reviews in the field of chemical engineering.

Sucrose fatty acid esters: synthesis, emulsifying capacities, biological activities and structure-property profiles

The notable physical and chemical properties of sucrose fatty acid esters have prompted their use in the chemical industry, especially as surfactants, since 1939. Recently, their now well-recognized value as nutraceuticals and as additives in cosmetics has significantly increased demand for ready access to them. As such a review of current methods for the preparation of sucrose fatty acid esters by both chemical and enzymatic means is warranted and is presented here together with an account of the historical development of these compounds as surfactants (emulsifiers). The somewhat belated recognition of the antimicrobial, anticancer and insecticidal activities of sucrose esters is also discussed along with a commentary on their structure-property profiles.

Ionic Liquids: Efficient Media for the Lipase-Catalyzed Michael Addition

Recently, ionic liquids (ILs) have been regarded as ideal media for non-aqueous bio-catalysis. In this work, the synthesis of warfarin by the lipase-catalyzed Michael addition in IL media and the parameters that affected the warfarin yield were investigated. Experimental results demonstrated that the chemical structures of the ILs were a major factor for influencing the warfarin yield. The ILs containing the NTf₂^– anion were suitable reaction media due to the high chemical stability of this anion. The incorporation of the hydroxyl group on the IL cation significantly improved the lipase activity due to the H₂O-mimicking property of this group. The lipase activity decreased by increasing the alkyl chain length on the IL cation due to the non-polar domain formation of the IL cation at the active site entrance of lipase. The ILs and lipase could be reused no less than five times without reduction in the warfarin yield.

Comparative Study of the Emulsifying Properties of a Homologous Series of Long-Chain 6'- O-Acylmaltose Esters

Emulsifiers derived from renewable resources such as sucrose and fatty acids are high volume commodity chemicals and currently produced by traditional chemical synthesis techniques that lack the capacity to form the most desirable monoesters (of sucrose) in a selective and efficient fashion. The development of new emulsifiers (surfactants) from alternate, structurally simpler but nevertheless abundant disaccharides such as maltose represents a possible solution to this problem. Herein, we report the facile enzymatic preparation of a homologous series of 6'- O-acylmaltose esters and an in-depth evaluation of them revealing that their surfactant properties and thermal stabilities are largely determined by the length of the fatty acid chain. In the first such comparison, we show that the foaming and emulsifying effects of certain of these maltose monoesters are superior to those of their sucrose-derived and commercially exploited counterparts. As such, maltose esters have considerable potential as emulsifiers for use in, for example, the food industry.

Recent developments in biocatalysis in multiphasic ionic liquid reaction systems

Ionic liquids are well known and frequently used 'designer solvents' for biocatalytic reactions. This review highlights recent achievements in the field of multiphasic ionic liquid-based reaction concepts. It covers classical biphasic systems including supported ionic liquid phases, thermo-regulated multi-component solvent systems (TMS) and polymerized ionic liquids. These powerful concepts combine unique reaction conditions with a high potential for future applications on a laboratory and industrial scale. The presence of a multiphasic system simplifies downstream processing due to the distribution of the catalyst and reactants in different phases.

Influence of the anion on the properties of ionic liquid mixtures: a molecular dynamics study

Big anions enhance the non-polar network in IL mixtures, while smaller ones win the competition for the imidazolium cation.

Enzymatic Synthesis of Glucose-Based Fatty Acid Esters in Bisolvent Systems Containing Ionic Liquids or Deep Eutectic Solvents

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.

Order in the chaos: the secret of the large negative entropy of dissolving 1-alkyl-3-methylimidazolium chloride in trihexyltetradecylphosphonium chloride

A large symmetric ion cluster cage is formed if 1-alkyl-3-methylimidazolium chloride ionic liquids with short alkyl chains are added to trihexyltetradecylphosphonium chloride which results in a large negative entropy of dissolution and an unexpected ion dynamics.