Natural Deep Eutectic Solvents as Performance Additives for Peroxygenase Catalysis

Abstract

Natural deep eutectic solvents (NADES) are proposed as alternative solvents for peroxygenase‐catalysed oxyfunctionalization reactions. Choline chloride‐based NADES are of particular interest as they can serve as solvent, enzyme‐stabiliser and sacrificial electron donor for the in situ H2O2 generation. This report provides the first proof‐of‐concept and basic characterisation of this new reaction system. Highly promising turnover numbers for the biocatalysts of up to 200,000 have been achieved.

Enantioselective Sulfoxidation of Thioanisole by Cascading a Choline Oxidase and a Peroxygenase in the Presence of Natural Deep Eutectic Solvents

“…First, we evaluated the influence of the water content in the DES reaction mixture (Figure ). In accordance to our previous findings with bienzymatic hydroxylation and epoxidation reactions, no sulfoxidation activity was found in neat DES and at least 25 % (v/v) of water (buffer) were necessary. This is, however, in stark contrast to previous findings on the perhydrolase‐catalysed reactions in DES .…”

“…The presence of ChCl‐based DES did not improve the stability or the activity of the biocatalysts. This is in stark contrast to previous findings on hydrolases in DES or even the An ChOx‐r Aae UPO‐system if used for hydroxylation and epoxidation reactions . This discrepancy calls for further studies aiming at more systematic investigation and understanding of the effects of DES on biocatalysts!…”

“…Interestingly, in buffer, the highest product formation was observed already at An ChOx concentrations as low as 3 μM whereas in the presence of 50 % (v/v) of ChCl‐Urea the overall productivity steadily increased over the entire An ChOx concentration range investigated. This may be attributed to the reduced activity of An ChOx in the presence of DES . In any case, it can be asserted that the H 2 O 2 generation rate (under these conditions) was overall rate limiting ( vide infra ).…”

“…Especially choline chloride (ChCl) is the basis of many (NA)DES. Recently, we have demonstrated that ChCl can be used not only as solvent component but also as sacrificial electron donor for the reductive activation of molecular oxygen by the enzyme choline oxidase from Arthrobacter nicotianae ( An ChOx) to promote perhydrolase‐ and peroxygenase‐catalysed oxyfunctionalisation reactions . Inspired by the recent contribution by Brenna and co‐workers on the peroxygenase‐catalysed sulfoxidation of thiols we became interested in expanding this reaction concept to ChCl‐based DES exploiting the dual functionality of these DES as co‐solvent and as co‐substrate (Figure and Figure ).…”

Biocatalyzed Redox Processes Employing Green Reaction Media

“…Thus, the choline chloride-based DESs can be employed as solvents and as electron donors. This oxidase has been combined with the peroxygenase from Agrocybe aegerita in order to perform effective biotransformations, including the hydroxylation of ethyl benzene ( 5 ) and the epoxidation of cis -β-methylstyrene ( 7 ) ( Scheme 21 ) [ 96 ]. Reactions cannot be developed in neat NADES, as no product formation was observed, being required some amount of buffer to ensure a proper enzymatic activity.…”