The effects of phenoloxidase inhibitors on the efficacy of malachite green decolorization by Azospirillum bacteria

Abstract

Synthetic dyes are widely used in various branches of light industry. Due to the insuffi cient effi ciency of industrial painting processes, a large percentage of dyes end up in the wastewater of enterprises in an unmodifi ed form, which creates a huge risk of environmental pollution with these compounds. Triphenylmethane dyes, in particular malachite green, are toxic, allergenic and carcinogenic compounds. To date, biodegradability of triphenylmethane dyes has been shown for some bacteria and fungi producing phenol oxidase complex enzymes, including soil associative bacteria of the genus Azospirillum. Many factors are capable of inducing and inhibiting the biodegradation effi ciency, in particular the enzymatic systems that are involved in bleaching processes. In the present work we studied the eff ects of typical deactivating agents of phenol oxidases, such as H2 O2 , EDTA, SDS-Na, β-mercaptoethanol, dithiothreitol, Tween, and sodium azide, on the azospirilla’s phenol oxidases activity and the ability to decolorize malachite green. It was found that Tween and sodium azide do not have an inhibitory eff ect on azospirillum enzymes and exhibit a total stabilizing eff ect on the entire complex. An inhibitory eff ect from 60 to 100% was noted for laccase and Mn-peroxidase activity under the action of β-mercaptoethanol, dithiothreitol and EDTA, which is directly proportional to the decolorization rate of malachite green. Compared with the latest issues on classical phenol-oxidizing enzymes, our data revealed non-typical properties of the phenol oxidase complex enzymes of azospirillum.

Keywords

• azospirillum
• phenol oxidases
• malachite green
• decolorization