Immobilization of D-amino acid oxidase via a biomimetic coating and its application for the production of 4-methylthio-2-oxobutyric acid

In this study, magnetic nanoparticles superficially modified with polydopamine were used for the immobilization of D-amino acid oxidases from Rhodosporidium toruloides (RtDAO) and Trigonopsis variabilis (TvDAO). The thermal and oxidative stabilities of RtDAO were improved significantly after immobilization; the T-m value was increased by 11 degrees C and the half-life in the presence of 10 mM hydrogen peroxide was increased by 42 min. However, in the case of TvDAO, these improvements in stability were not observed. The activities of immobilized RtDAO and TvDAO were lowered to approximately 50% after sixteen and five repeated operations, respectively, indicating that the former had better reusability. Immobilized TvDAO was further applied to the conversion of P-methionine to 4-methylthio-2-oxobutyric acid (MTOB). Without the addition of catalase, most MTOB produced was spontaneously oxidized to 3-methylthiopropionic acid by hydrogen peroxide. With the addition of 1600 U of catalase, the conversion reached 100% after a 10 min-incubation with the product entirely in the form of MTOB. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.