The atmospheric pressure capillary plasma jet is well-suited to supply H2O2 for plasma-driven biocatalysis

Abstract

Plasma-generated H2O2 can be used to fuel biocatalytic reactions that require H2O2 as co-substrate such as the conversion of ethylbenzene to (R)-1-phenylethanol ((R)-1-PhOl) catalyzed by unspecific peroxygenase from Agrocybe aegerita (rAaeUPO). Immobilization was recently shown to protect biocatalysts from inactivation by highly reactive plasma-produced species, however, H2O2 supply by the employed plasma sources ({micro}APPJ and DBD) was limiting for rAaeUPO performance. In this study we evaluated a recently introduced capillary plasma jet for suitability to supply H2O2 in situ. H2O2 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-1rAaeUPO was achieved without significant enzyme inactivation. By exchanging the reaction solution every 5 min, a total product yield of 122 {micro}mol (R)-1-PhOl was achieved in 700 min run time, resulting in a total turnover number of 174,209 mol(R)-1-PhOl mol-1rAaeUPO. We conclude that the capillary plasma jet, due to its flexibility regarding feed gas, admixtures, and power input, is well-suited for in situ H2O2 generation for plasma-driven biocatalysis tailoring to enzymes with high H2O2 turnover.