Biochemical and molecular characterization of a novel dye-decolourizing peroxidase from Raoultella ornithinolytica OKOH-1

Abstract

The increase in industrial demand for peroxidases has necessitated the search for novel peroxidase with excellent industrial versatility. Raoultella ornithinolytica OKOH-1 is a new ligninolytic bacteria with peroxidase production potential. However, there is paucity of information on characterization of peroxidase from Raoultella species and its application potential in bioremediation. In this study, we characterized peroxidase from Raoultella ornithinolytica OKOH-1 (RaoPrx) for the first time using biochemical approach and bioinformatics; and as well investigated the dye-decolourization potential of the enzyme. RaoPrx oxidized various substrates, with pyrogallol giving the optimum activity. It had an optimum activity at pH 6 and was stable over a pH range of 5.0-7.0 with residual activity of above 40% after 120 min of incubation. The enzyme showed an optimum activity at 50 °C and was very stable at higher temperatures (50-70 °C) with residual activity of above 70% after 120 min. The enzyme was remarkably stable at 50 °C as it retained over 90% of its original activity after 120 min. The peroxidase activity was enhanced by Ag⁺, Cu^2+, Zn²⁺and Fe²⁺, but was inhibited by Ca^2+, Mg^2+, Ba^2+, Al³⁺, Co²⁺, NaN₃ and EDTA. Furthermore, molecular characterization suggests RaoPrx as a novel dye-decolourizing peroxidase (DyP-type) family belonging to Class B, with estimated mo1ecular weight of 17.587 kDa and isoelectric point of 4.51, this is further confirmed by its remarkable dye-decolourizing activity on congo red and melanin in this study. This, therefore, indicates its application potential in textile dyes remediation and development of cosmetic agent.

Keywords: DyP-type peroxidase; Enzyme characterization; Peroxidase gene.