Solvent‐Free Photobiocatalytic Hydroxylation of Cyclohexane

Abstract

The use of neat reaction media, that is the avoidance of additional solvents, is the simplest and the most efficient approach to follow in biocatalysis. Here, we show that unspecific peroxygenase from Agrocybe aegerita (AaeUPO) can hydroxylate the neat model substrate cyclohexane. H2O2 was photocatalytically generated in situ by nitrogen‐doped carbon nanodots (N−CNDs) and UV LED illumination. AaeUPO entrapment in alginate beads increased enzyme stability and facilitated the reaction in neat cyclohexane. N−CNDs absorption in beads containing AaeUPO created a 2‐in‐1 heterogeneous photobiocatalyst that was active for up to seven days under reaction conditions and produced cyclohexanol, 2.5 mM. To increase productivity, the bead size and the photocatalyst‐to‐enzyme ratio have been identified as promising targets for optimisation.

Applied biocatalysis beyond just buffers – from aqueous to unconventional media. Options and guidelines

“…In two recent examples, peroxygenases were applied in neat conditions, with the enzyme immobilized either on carriers or in alginate beads. 57,58 A variant of this approach is when the combination of two substrates create deep eutectic systems, as Pätzold and co-workers have shown for the esterification of menthol with lauric acid with a conversion of up to 95%. 59 Finally, in an industrial example by Enzymaster, an engineered transaminase 60 in whole cells was able to catalyze the formation of (R)-phenyl ethylamine from a solution of pure acetophenone and isopropylamine.…”

Photo‐biocatalytic Cascades: Combining Chemical and Enzymatic Transformations Fueled by Light

“…[59] However, due to their sensitivity towards H 2 O 2 , their implementation in large-scale applications is still challenging. [59,60] Recent studies proposed the light-driven in situ generation of H 2 O 2 as a promising approach [36,[61][62][63][64][65] exhibiting improved atom efficiency compared to the conventional enzyme-catalyzed cosubstrate supply. [66] Thereby, light exposure of organic or TiO 2 -based photocatalysts in the presence of a suitable electron donor yields in the formation of photoexcited reducing equivalents, capable of the subsequent reduction of O 2 to the stoichiometric oxidant H 2 O 2 .…”

An alginate-confined peroxygenase-CLEA for styrene epoxidation

“…While a limited number of studies report immobilisation of peroxygenases, this technique is not fully explored yet for this enzyme class. [7][8][9][10][11][12] In previous works, we could demonstrate that immobilised peroxygenases in principle can even be applied in neat (i.e. almost water-free) reaction media.…”

“…The so-confined enzymes are mechanically stabilised while still situated in a micro-aqueous environment. 8,11,13 We therefore set out to immobilise a peroxygenase in an alginate matrix and evaluate its catalytic activity under non aqueous reaction conditions. As model enzyme we chose the recombinantly expressed, evolved peroxygenase from Agrocybe aegerita (rAaeUPO) [14][15][16] as catalyst for the epoxidation of styrene and cis-b-methylstyrene (Scheme 2).…”

“…The so-confined enzymes are mechanically stabilised while still situated in a micro-aqueous environment. 8,11,13 …”