The atmospheric pressure capillary plasma jet is well-suited to supply H ₂ O ₂ for plasma-driven biocatalysis

Plasma-generated H ₂ O ₂ can be used to fuel biocatalytic reactions that require H ₂ O ₂ as co-substrate such as the conversion of ethylbenzene to ( R )-1-phenylethanol (( R )-1-PhOl) catalyzed by unspecific peroxygenase from Agrocybe aegerita (r Aae UPO). Immobilization was recently shown to protect biocatalysts from inactivation by highly reactive plasma-produced species, however, H ₂ O ₂ supply by the employed plasma sources (µAPPJ and DBD) was limiting for r Aae UPO performance. In this study we evaluated a recently introduced capillary plasma jet for suitability to supply H ₂ O ₂ in situ . H ₂ O ₂ production was modulated by varying the water concentration in the feed gas, providing a greater operating window for applications in plasma-driven biocatalysis. In a static system after 80 min of biocatalysis, a turnover number of 44,199 mol _{( R )-1-PhOl} mol ^-1 _{r Aae UPO} was achieved without significant enzyme inactivation. By exchanging the reaction solution every 5 min, a total product yield of 122 µmol ( R )-1-PhOl was achieved in 700 min run time, resulting in a total turnover number of 174,209 mol _{( R )-1-PhOl} mol ^-1 _{r Aae UPO} . We conclude that the capillary plasma jet, due to its flexibility regarding feed gas, admixtures, and power input, is well-suited for in situ H ₂ O ₂ generation for plasma-driven biocatalysis tailoring to enzymes with high H ₂ O ₂ turnover.