Performance of d-amino acid oxidase in presence of ionic liquids

The activity and stability of free and immobilized d-amino acid oxidase (DAAO, EC 1.4.3.3) from Trigonopsis variabilis CBS 4095 in different water-soluble and water-insoluble ionic liquids (ILs) as well as in organic solvents were studied for comparison. The most promising ILs ([BMIM][BF4] and [MMIM][MMPO4]) were investigated in detail. The kinetic parameters (vmaxvmax = 187 nkat/g dry weight, KM = 1.38 mM) with d-phenylalanine as substrate were calculated in 40% [BMIM][BF4]. Bioconversions of d/l-phenylalanine in 40% [BMIM][BF4] and 20% [MMIM][MMPO4] on a 3 ml scale using immobilized DAAO were performed by addition of free catalase from Micrococcus lysodeikticus. After total conversion of substrate in presence of 20% [MMIM][MMPO4] the residual activity of the immobilized DAAO was 79% and 100% of the free catalase.