Mineralization of sulfonated azo dyes and sulfanilic acid by Phanerochaete chrysosporium and Streptomyces chromofuscus

Abstract

Five "4C-radiolabeled azo dyes and sulfanilic acid were synthesized and used to examine the relationship between dye substitution patterns and biodegradability (mineralization to C02) by a white-rot fungus and an actinomycete. 4-Amino-[U-14Cjbenzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-'4Clbenzenesulfonic acid were used as representative compounds having sulfo groups or both sulfo and azo groups. Such compounds are not known to be present in the biosphere as natural products. The introduction of lignin-like fragments into the molecules of 4-amino-[U-14Clbenzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-14C]benzenesulfonic acid by coupling reactions with guaiacol (2-methoxyphenol) resulted in the formation of the dyes 4-(3-methoxy-4-hydroxyphenylazo)-[U-14C]benzenesulfonic acid and 4-(2-sulfo-3'-methoxy-4'-hydroxy-azobenzene4-azo)-[U-14Clbenzenesulfonic acid, respectively. The synthesis of acid azo dyes 4-(2hydroxy-l-naphthylazo)-[U-14Cjbenzenesulfonic acid and 4-(4-hydroxy-l-naphthylazo)-[U-_4C]benzenesulfonic acid also allowed the abilities of these microorganisms to mineralize these commercially important compounds to be evaluated. Phanerochaete chrysosporium mineralized all of the sulfonated azo dyes, and the substitution pattern did not significantly influence the susceptibility of the dyes to degradation. In contrast, Streptomyces chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups. However, it mediated the mineralization of modified dyes containing lignin-like substitution patterns. This work showed that lignocellulolytic fungi and bacteria can be used for the biodegradation of anionic azo dyes, which thus far have been considered among the xenobiotic compounds most resistant to biodegradation. Very specific structural changes in the azo dye molecules enhanced their biodegradability.

Investigation of the Toxicity of the Products of Decoloration of Amaranth by Trametes versicolor

“…Th e fact that the toxicity of the treatment continued to decrease from Day 12 to Day 24 to control's value (when considering the confi dence interval) suggests that these metabolites suff er further transformation into fragments that are as nontoxic as natural fungal metabolites released by the mycelium. Th ese observations are consistent with the mechanism of Amaranth decoloration by T. versicolor proposed by Gavril and Hodson (2007b) and with the reports regarding the mechanism of degradation (Spadaro and Renganathan, 1994) and mineralization (Paszczynski et al, 1992) of various azo dyes by another member of the white-rot fungi family, Phanarochaete chrysosporium. Th ese researchers suggest that the dyes are reduced to smaller molecular mass compounds similar in structure to the compounds of fungal metabolism (Gavril and Hodson, 2007b) or to CO 2 and water (Paszczynski et al, 1992).…”

Degradation of Azo Dyes by Environmental Microorganisms and Helminths

“…The biochemical pathway or pathways of azo dye biodegradation idare poorly understood. This [69] showed that P. chrysosporium mineralized many sulfonated azo dyes and that modification of the chemical structure of these dyes did not significantly influence their susceptibility to degradation. In contrast, S. chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups [69].…”

“…This [69] showed that P. chrysosporium mineralized many sulfonated azo dyes and that modification of the chemical structure of these dyes did not significantly influence their susceptibility to degradation. In contrast, S. chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups [69]. They also showed that peroxidase enzymes were involved in the initial azo dye biodegradation process [70].…”

Microbial desulfonation

“…Desulfonations of aromatic sulfonates in fungi have also been implied, because CO P from the ring carrying the sulfonate was released [112], or observed directly [113]. These reactions have been attributed to (extracellular) peroxidases [113,114], which sometimes lead to extensive destruction of the compounds involved, essentially as in the enzymic combustion of lignin [115].…”