Phylogenetically diverse bacteria isolated from tattoo inks, an azo dye-rich environment, decolorize a wide range of azo dyes

Seong Won Nho,Huizhong Chen,Jinshan Jin,Seong-Jae Kim,Xuewen Cui,Mi Sun Moon,Ohgew Kweon,Carl E Cerniglia

doi:10.1186/s13213-021-01648-2

Abstract

PurposeThere has been an interest in the microbial azo dye degradation as an optional method for the treatment of azo dye-containing wastes. Tattoo ink is an extremely unique azo dye-rich environment, which have never been explored in terms of microorganisms capable of degrading azo dyes. Previously, we isolated 81 phylogenetically diverse bacteria, belonging to 18 genera and 52 species, contaminated in tattoo inks. In this study, we investigated if these bacteria, which can survive in the azo dye-rich environment, have an ability to degrade azo dyes.MethodsWe conducted a two-step azo dye degradation (or decolorization) assay. In step 1, a high-throughput degradability assay was done for 79 bacterial isolates using Methyl Red and Orange II. In step 2, a further degradation assay was done for 10 selected bacteria with a representative of 11 azo dyes, including 3 commercial tattoo ink azo dyes. Degradation of azo dyes were calculated from measuring optical absorbance of soluble dyes at specific wavelengths.ResultsThe initial high-throughput azo dye assay (step 1) showed that 79 isolates had a complete or partial degradation of azo dyes; > 90% of Methyl Red and Orange II were degraded within 24 h, by 74 and 20 isolates, respectively. A further evaluation of azo dye degradability for 10 selected isolates in step 2 showed that the isolates, belonging to Bacillus, Brevibacillus, Paenibacillus, and Pseudomonas, exhibited an excellent decolorization ability for a wide range of azo dyes.ConclusionsThis study showed that phylogenetically diverse bacteria, isolated from azo dye-rich tattoo inks, is able to degrade a diverse range of azo dyes, including 3 azo dyes used in commercial tattoo inks. Some of the strains would be good candidates for future studies to provide a systematic understanding of azo dye degradation mechanisms.

Highlights

Azo dyes, which are the most common class of dyes containing one or more azo (–N=N–) bonds, are widely used in textile, paper, cosmetic, pharmaceutical, and food industries (Carmen and Daniela 2012)
This study showed that phylogenetically diverse bacteria, isolated from azo dye-rich tattoo inks, is able to degrade a diverse range of azo dyes, including 3 azo dyes used in commercial tattoo inks
A two-step strategy was used in this study; initially degradation of azo dye was tested for all tattoo inkderived bacterial isolates using Methyl Red and Orange II, followed by an evaluation of selected bacteria with respect to the degradation of 11 representative azo dyes, including 3 commercial tattoo ink azo dyes (Fig. 1)

Summary

Introduction

Azo dyes, which are the most common class of dyes containing one or more azo (–N=N–) bonds, are widely used in textile, paper, cosmetic, pharmaceutical, and food industries (Carmen and Daniela 2012). Industries release large amount of insufficiently treated azo dye-containing waste in the environment (Rawat et al 2016). Physicochemical-based methods, such as absorption, coagulation, precipitation, chemical transformation, and incineration, have often been used for the remediaion of azo dyes-containing waste effluents in the environment (Robinson et al 2001). These methods have limited applicability due to lack of efficiency, high cost, generation of toxic by-products, and high energy requirements. Biotechnological methods using microorganisms have been suggested as an option to overcome the limitations of the physicochemical-based approaches for the reduction of azo dyes in the environment (Forgacs et al 2004; Robinson et al 2001). Diverse categories of microorganisms, including bacteria, fungi, and algae, have been reported to be capable of degrading a wide range of azo dyes (Solís et al 2012; Stolz 2001)

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Results

Conclusion