Bacterial degradation of anthraquinone dyes

Abstract

Anthraquinone dyes, which contain anthraquinone chromophore groups, are the second largest class of dyes after azo dyes and are used extensively in textile industries. The majority of these dyes are resistant to degradation because of their complex and stable structures; consequently, a large number of anthraquinone dyes find their way into the environment causing serious pollution. At present, the microbiological approach to treating printing and dyeing wastewater is considered to be an economical and feasible method, and reports regarding the bacterial degradation of anthraquinone dyes are increasing. This paper reviews the classification and structures of anthraquinone dyes, summarizes the types of degradative bacteria, and explores the possible mechanisms and influencing factors of bacterial anthraquinone dye degradation. Present research progress and existing problems are further discussed. Finally, future research directions and key points are presented.

Keywords: Anthraquinone dyes; Bacterial degradation; Degradation mechanism; Influencing factor.

Table 1

Basic structures of several anthraquinone dyes

Fig. 1

Stepwise procedure for isolating dye-degrading strains under laboratory conditions

Fig. 2

Proposed pathway for the biotransformation of Reactive Blue 4 by aerobic bacterial granules (ABGs) This figure is modified from Chaudhari et al. (2017)

Fig. 3

Proposed pathway of 1-amino-4-bromoanthraquinone-2-sulfonic acid degradation by Sphingomonas herbicidovorans FL This figure is modified from Fan et al. (2008)

Fig. 4

Crystal structures of VcDyP (a) α-Helices and β-sheets of a VcDyP subunit are colored red and yellow, respectively. The heme is colored pink. (b) Close-up of the heme-binding site and putative pH-dependent radical transfer pathways at a lower pH (1) and higher pH (2). Reprinted with permission from Uchida et al. (2015), copyright 2015, American Chemical Society