Can Deep Eutectic Solvents Sustain Oxygen-Dependent Bioprocesses?—Measurements of Oxygen Transfer Rates

Abstract

The oxygen transfer rate (OTR) of dioxygen to solutions describing the transport of oxygen gas from the gaseous phase into the liquid phase of a reaction system over a given period is an important measure for biotechnological applications. The OTRs have already been described for aqueous systems and also recently for organic and non-conventional media, whereas the OTRs of a novel class of solvents, deep eutectic solvents (DESs), have not been determined yet. In this contribution, we report for the first time on the OTRs of choline chloride:ethylene glycol (ChCl:EG, 'ethaline') and ethylammonium chloride:ethylene glycol (EAC:EG, 'ethethylaline') while using water as a reference. We applied the dynamic measurement method and found up to 11-fold lower volumetric mass transfer coefficient (kLa) for ethaline and 6-fold lower for ethethylaline when compared to water at 25°C. Furthermore, we investigated the effect temperature (35°C and 45°C) has on the kLa for those solvents. File list (2) download file view on ChemRxiv 2021-03-03_ChemRxiv_Manuscript.pdf (508.61 KiB) download file view on ChemRxiv 2021-03-03_ChemRxiv_SuppInfo.pdf (664.82 KiB) Can deep eutectic solvents sustain oxygen dependent bioprocesses? -Measurements of oxygen transfer rates

Radical-mediated thiol–ene ‘click’ reactions in deep eutectic solvents for bioconjugation

“…Recently, the oxygen transfer rate for a number of DESs has been investigated, including study of the potential scope for tailoring reaction conditions to favour oxygen solvation. 38 Of particular influence on this factor is the viscosity of the solvent, which can be readily influenced through heating or addition of water. Furthermore, increased stirring has been shown to improve yield in oxygen-dependent reactions for DESs.…”

“…Furthermore, the addition of a small amount of water as co-solvent was applied to select examples (see ESI†), providing lower viscosity and also increasing the oxygen transfer rate. 38 The oxygen-mediated conditions were first applied to simple thiol ( 8 ) and thioacid ( 17 ) examples for investigation of compatibility and efficiency. Of particular note is the result obtained for alkyl bromide example 18 , in which bromide substitution products were not observed.…”

Selective Aerobic Oxidation of Alcohols in Low Melting Mixtures and Water and Use for Telescoped One‐Pot Hybrid Reactions

“…Interestingly, Kara and co‐workers recently reported the results of a study on the feasibility of transferring dioxygen from air into DESs, while using water as a reference, demonstrating that the nature of DESs had big influences on the oxygen transfer. [17] We wondered whether the oxidation of alcohols could also be achieved directly in DESs with air as the terminal oxidant. Thus, we screened again the oxidation of 1 a to 2 a in the presence of the CuCl 2 /TEMPO/TMEDA system in some representative DES mixtures and under the best conditions found for the oxidation in water (Table 1 , entry 4).…”

“…Interestingly, Kara and co‐workers recently reported the results of a study on the feasibility of transferring dioxygen from air into DESs, while using water as a reference, demonstrating that the nature of DESs had big influences on the oxygen transfer [17] . We wondered whether the oxidation of alcohols could also be achieved directly in DESs with air as the terminal oxidant.…”

Deep Eutectic Solvents for the Enzymatic Synthesis of Sugar Esters: A Generalizable Strategy?

“…Because of the formation of intermolecular hydrogen bonds, the melting point of the mixture decreases sharply, and DESs are liquid and stable at room temperature. Owing to the vast variety of possible HBDs and HBAs, the possibility of changing the components’ ratio, and the amount of external water added, the potential number of combinations is immense, which confers them a high degree of tunability . Moreover, it is possible to appropriately select the components to prepare non-toxic and highly biodegradable DESs. , These solvents have nowadays a wide range of applications ranging from solvents for reactions, extraction, gas capture and separation, and (bio)­catalysis. − The remaining challenges for DESs are mainly associated with their high viscosity, which affects the mass transfer in the reaction and adds complexity to the downstream processing.…”