Lipase-Catalyzed Production of Sorbitol Laurate in a “2-in-1” Deep Eutectic System: Factors Affecting the Synthesis and Scalability

Abstract

Surfactants, such as glycolipids, are specialty compounds that can be encountered daily in cleaning agents, pharmaceuticals or even in food. Due to their wide range of applications and, more notably, their presence in hygiene products, the demand is continuously increasing worldwide. The established chemical synthesis of glycolipids presents several disadvantages, such as lack of specificity and selectivity. Moreover, the solubility of polyols, such as sugars or sugar alcohols, in organic solvents is rather low. The enzymatic synthesis of these compounds is, however, possible in nearly water-free media using inexpensive and renewable building blocks. Using lipases, ester formation can be achieved under mild conditions. We propose, herein, a “2-in-1” system that overcomes solubility problems, as a Deep Eutectic System (DES) made of sorbitol and choline chloride replaces either a purely organic or aqueous medium. For the first time, 16 commercially available lipase formulations were compared, and the factors affecting the conversion were investigated to optimize this process, owing to a newly developed High-Performance Liquid Chromatography-Evaporative Light Scattering Detector (HPLC-ELSD) method for quantification. Thus, using 50 g/L of lipase formulation Novozym 435® at 50 °C, the optimized synthesis of sorbitol laurate (SL) allowed to achieve 28% molar conversion of 0.5 M of vinyl laurate to its sugar alcohol monoester when the DES contained 5 wt.% water. After 48h, the de novo synthesized glycolipid was separated from the media by liquid–liquid extraction, purified by flash-chromatography and characterized thoroughly by one- and two-dimensional Nuclear Magnetic Resonance (NMR) experiments combined to Mass Spectrometry (MS). In completion, we provide initial proof of scalability for this process. Using a 2.5 L stirred tank reactor (STR) allowed a batch production reaching 25 g/L in a highly viscous two-phase system.

Enzymatic Synthesis of Alkyl Glucosides byβ‐Glucosidases in a 2‐in‐1 Deep Eutectic Solvent System

“…Enzymes require a minimal amount of water to maintain their hydration shell and stay active. This behavior observed is not singular to ß-glucosidases, indeed, lipases were also reported to exhibit the need for a minimum amount of water in a similar range of concentration (5-10 wt %) [33,36,40]. However, the investigated ß-glucosidases operate at relatively low water content compared to other glycosidic enzymes as for example, a-amylases required at least 10-20 % of water as co-solvent to show activity [20].…”

“…Deep eutectic solvents (DES) that are made from inexpensive renewable raw materials [30] are an interesting alternative to organic solvents [25] or ionic liquids [26]. After the successful demonstration of various sugar synthons esterification with different fatty acid building blocks employing lipases in DES [39,40], whereby the sugar component can act as a solvent component and as a substrate at the same time [33,35,36,40], this study showed that glycosidases can also be used in DES for the synthesis of AGs according to the 2-in-1 concept. In other studies, presented so far, DES had mainly been used as a co-solvent [26][27][28][29].…”

“…Besides having beneficial effects on stability and activity of enzymes, DESs can also be used as 2-in-1 systems. For glycolipid synthesis with lipases in DES, it was shown that either the fatty acid or the sugar component can be part of the hydrophobic or hydrophilic DES, respectively, but at the same time also be a substrate for the enzymatic reaction [31][32][33][34][35][36]. Aim of the presented study is to transfer this concept to b-glucosidase reactions.…”

Lipase-Mediated Mechanoenzymatic Synthesis of Sugar Esters in Dissolved Unconventional and Neat Reaction Systems

“… 18 − 20 Nonetheless, these compounds are of great interest in the food-, cosmetic-, and pharmaceutical industry. For example, sorbitol-6- O -laurate, a model compound studied by Delavault et al, 21 is structurally related to an emulsifier registered as E493, which is commonly employed for pharmaceutical and food applications and approved by the European Food Safety Authority (EFSA). 22 Enzymatic synthesis of glycolipids provides an alternative to chemical synthesis as milder conditions are applicable, for example, relatively low temperature, as well as selective synthesis, which reduces side product formation.…”

“…However, the chemical procedure requires the use of harsh conditions like high temperature, acidic catalysis (e.g., by perfluorinated alkylsulfonic acid), and complicated processing requiring multiple steps of protection, deprotection, and activation (e.g., with allyl, benzyl, and p -methoxybenzyl groups), leading to wasteful side products. − Nonetheless, these compounds are of great interest in the food-, cosmetic-, and pharmaceutical industry. For example, sorbitol-6- O -laurate, a model compound studied by Delavault et al, is structurally related to an emulsifier registered as E493, which is commonly employed for pharmaceutical and food applications and approved by the European Food Safety Authority (EFSA) . Enzymatic synthesis of glycolipids provides an alternative to chemical synthesis as milder conditions are applicable, for example, relatively low temperature, as well as selective synthesis, which reduces side product formation .…”