Enzymatic halogenation and oxidation using an alcohol oxidase-vanadium chloroperoxidase cascade

The chemo-enzymatic cascade which combines alcohol oxidase from Hansenula polymorpha (AOXHp) with vanadium chloroperoxidase (VCPO), for the production of biobased nitriles from amino acids was investigated. In the first reaction H2O2 (and acetaldehyde) are generated from ethanol and oxygen by AOXHp. H2O2 is subsequently used in the second reaction by VCPO to produce HOBr in situ. HOBr is required for the non-enzymatic oxidative decarboxylation of glutamic acid (Glu) to 3-cyanopropanoic acid (CPA), an intermediate in the production of biobased acrylonitrile. It was found that during the one pot conversion of Glu to CPA by AOXHp-VCPO cascade, AOXHp was deactivated by HOBr. To avoid deactivation, the two enzymes were separated in two fed-batch reactors. The deactivation of AOXHp by HOBr appeared to depend on the substrate: an easily halogenated compound like monochlorodimedone (MCD) was significantly converted in one pot by the cascade reaction of AOXHp and VCPO, while conversion of Glu did not occur under those conditions. Apparently, MCD scavenges HOBr before it can inactivate AOXHp, while Glu reacts slower, leading to detrimental concentrations of HOBr. Enzymatically generated H2O2 was used in a cascade reaction involving halogenation steps to enable the co-production of biobased nitriles and acetaldehyde.