Lipase‐Catalyzed Synthesis of Saccharide–Fatty Acid Esters Using Suspensions of Saccharide Crystals in Solvent‐Free Media

Latest Trends in Lipase-Catalyzed Synthesis of Ester Carbohydrate Surfactants: From Key Parameters to Opportunities and Future Development

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.

A review on the synthesis of bio-based surfactants using green chemistry principles

OBJECTIVES

With increasing awareness of the potential adverse impact of conventional surfactants on the environment and human health, there is mounting interest in the development of bio-based surfactants (which are deemed to be safer, more affordable, are in abundance, are biodegradable, biocompatible and possess scalability, mildness and performance in formulation) in personal care products.

METHOD

A comprehensive literature review around alkyl polyglucosides (APGs) and sucrose esters (SEs) as bio-based surfactants, through the lens of the 12 green chemistry principles was conducted. An overview of the use of bio-based surfactants in personal care products was also provided.

RESULTS

Bio-based surfactants are derived primarily from natural sources (i.e. both the head and tail molecular group). One of the more common types of bio-based surfactants are those with carbohydrate head groups, where alkyl polyglucosides (APGs) and sucrose esters (SEs) lead this sub-category. As global regulations and user mandate for sustainability and safety increase, evidence to further support these bio-based surfactants as alternatives to their petrochemical counterparts is advantageous. Use of the green chemistry framework is a suitable way to do this. While many of the discussed principles are enforced industrially, others have only yet been applied at a laboratory scale or are not apparent in literature.

CONCLUSION

Many of the principles of green chemistry are currently used in the synthesis of APGs and SEs. These and other bio-based surfactants should, therefore, be considered suitable and sustainable alternatives to conventional surfactants. To further encourage the use of these novel surfactants, industry must make an effort to implement and improve the use of the remaining principles at a commercial level.

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.

Solvent-Free Approaches in Carbohydrate Synthetic Chemistry: Role of Catalysis in Reactivity and Selectivity

Owing to their abundance in biomass and availability at a low cost, carbohydrates are very useful precursors for products of interest in a broad range of scientific applications. For example, they can be either converted into basic chemicals or used as chiral precursors for the synthesis of potentially bioactive molecules, even including nonsaccharide targets; in addition, there is also a broad interest toward the potential of synthetic sugar-containing structures in the field of functional materials. Synthetic elaboration of carbohydrates, in both the selective modification of functional groups and the assembly of oligomeric structures, is not trivial and often entails experimentally demanding approaches practiced by specialized groups. Over the last years, a large number of solvent-free synthetic methods have appeared in the literature, often being endowed with several advantages such as greenness, experimental simplicity, and a larger scope than analogous reactions in solution. Most of these methods are catalytically promoted, and the catalyst often plays a key role in the selectivity associated with the process. This review aims to describe the significant recent contributions in the solvent-free synthetic chemistry of carbohydrates, devoting a special critical focus on both the mechanistic role of the catalysts employed and the differences evidenced so far with corresponding methods in solution.

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.

Immobilized lipase catalyzing glucose stearate synthesis and their surfactant properties analysis

Sugar fatty acid esters are practical importance and have a variety of applications that include surfactants and as an emulsifying agent. In this study, we report glucose stearate synthesis using lipase-Fe₃O₄ nanoparticles catalyst. The influence of various reaction factors, such as silica gel concentration, molar ratio of sugar/acid, reaction temperature and speed of agitation on esterification by immobilized enzyme was analyzed. The glucose stearate esterification degree of 87.2 % was obtained under the optimized condition: 1:2 molar ratio of glucose/stearic acid, 2 % (w/v) of silica gel at 120 rpm and 40 °C. Glucose esters were characterized according to their surfactant activity like emulsification index, oil displacement activity and antimicrobial activity. The results indicated glucose stearate acts as biosurfactant, with emulsification index of 66 % in mustard oil and oil displacement activity of 19.64 cm².

Incorportation of Ethyl Esters of EPA and DHA in Soybean Lecithin Using Rhizomucor miehei Lipase: Effect of Additives and Solvent-Free Conditions

The transesterification of soybean lecithin with ethyl esters of polyunsaturated fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)) using immobilized lipase from Rhizomucor miehei was tested in the presence or absence of organic solvent (hexane) and additives (urea with Ca(2+) or Mg(2+)). The reaction was carried out at a water concentration of 4 % and ethyl ester to phospholipid mass ratio of 3:1. After 24 h of reaction without solvent or additive, fatty acid incorporation reached 29.1 % and thereafter increased only slightly. After 48 h, incorporation was highest in the presence of Mg(2+), urea, and solvent. After 72 h, it was highest with Mg(2+) and urea in the presence or absence of solvent (56.8 and 45.7 %, respectively). Incorporation of EPA and DHA was thus initially fast without solvent and additive, but was increased after prolonged reaction in the presence of Mg(2+) and urea with or without solvent. These results are innovative and promising since they show that immobilized Rhizomucor miehei lipase has potential as a biocatalyst for interesterification reactions without solvent.

Solvent-Free Synthesis of Flavour Esters through Immobilized Lipase Mediated Transesterification

The synthesis of methyl butyrate and octyl acetate through immobilized Rhizopus oryzae NRRL 3562 lipase mediated transesterification was studied under solvent-free conditions. The effect of different transesterification variables, namely, molarity of alcohol, reaction time, temperature, agitation, addition of water, and enzyme amount on molar conversion (%) was investigated. A maximum molar conversion of 70.42% and 92.35% was obtained in a reaction time of 14 and 12 h with the transesterification variables of 0.6 M methanol in vinyl butyrate and 2 M octanol in vinyl acetate using 80 U and 60 U immobilized lipase with the agitation speed of 200 rpm and 0.2% water addition at 32°C and 36°C for methyl butyrate and octyl acetate, respectively. The immobilized enzyme has retained good relative activity (more than 95%) up to five and six recycles for methyl butyrate and octyl acetate, respectively. Hence, the present investigation makes a great impingement in natural flavour industry by introducing products synthesized under solvent-free conditions to the flavour market.

Thermo-kinetics of lipase-catalyzed synthesis of 6-O-glucosyldecanoate

Lipase-catalyzed synthesis of 6-O-glucosyldecanoate from d-glucose and decanoic acid was performed in dimethyl sulfoxide (DMSO), a mixture of DMSO and tert-butanol and tert-butanol alone with a decreasing order of polarity. The highest conversion yield (> 65%) of decanoic acid was obtained in the blended solvent of intermediate polarity mainly because it could dissolve relatively large amounts of both the reactants. The reaction obeyed Michaelis-Menten type of kinetics. The affinity of the enzyme towards the limiting substrate (decanoic acid) was not affected by the polarity of the solvent, but increased significantly with temperature. The esterification reaction was endothermic with activation energy in the range of 60-67 kJ mol⁻¹. Based on the Gibbs energy values, in the solvent blend of DMSO and tert-butanol the position of the equilibrium was shifted more towards the products compared to the position in pure solvents. Monoester of glucose was the main product of the reaction.