Microbial degradation of azo dyes

Azo dyes have become a staple in various industries, as colors play an important role in consumer choices. However, these dyes pose various health and environmental risks. Although different wastewater treatments are available, the search for more eco-friendly options persists. Bioremediation utilizing microorganisms has been of great interest to researchers and industries, as the transition toward greener solutions has become more in demand through the years. This review tackles the health and environmental repercussions of azo dyes and its metabolites, available biological approaches to eliminate such dyes from the environment with a focus on the use of different microorganisms, enzymes that are involved in the degradation of azo dyes, and recent trends that could be applied for the treatment of azo dyes

In vitro and in silico analysis of Brilliant Black degradation by Actinobacteria and a Paraburkholderia\it Paraburkholderia sp.

The soil bacteria isolated in this study, including three strains of actinobacteria and one $\it Paraburkholderia$ sp., showed decolorization activity of azo dyes in the resting cell assay and were shown to use methyl red as the sole carbon source to proliferate. Therefore, their ability to degrade, bioabsorb, or a combination of both mechanism was investigated using the substrate brilliant black. The strains DP-A9 and DP-L11, within 24 h of incubation, showed complete biodegradation of 173.54 mg/L brilliant black and the strains DP-D10 and DP-P12 showed partial decolorization of 83.3 mg/L and 36.4 mg/L, respectively, by both biosorption and biodegradation. In addition, the shotgun assembled genome of these strains showed a highly diverse set of genes encoding for candidate dye degrading enzymes, providing avenues to study azo dye metabolism in more detail

Improving biocatalytic properties of an azoreductase via\it via the N\it N-terminal fusion of formate dehydrogenase

Azoreductases require NAD(P)H to reduce azo dyes but the high cost of NAD(P)H limits its application. Formate dehydrogenase (FDH) allows $NAD(P)^{+}$ recycling and therefore, the fusion of these two biocatalysts seems promising. This study investigated the changes to the fusion protein involving azoreductase (AzoRo) of $\textit {Rhodococcus opacus}$ 1CP and FDH ($FDH_{C23S}$ and $FDH_{C23SD195QY196H}$) of $\textit {Candida boidinii}$ in different positions with His-tag as the linker. The position affected enzyme activities as AzoRo activity decreased by 20-fold when it is in the $\it N$-terminus of the fusion protein. $FDH_{C23S}$+ AzoRo was the most active construct and was further characterized. Enzymatic activities of $FDH_{C23S}$+ AzoRo decreased compared to parental enzymes but showed improved substrate scope – accepting bulkier dyes. Moreover, pH has an influence on the stability and activity of the fusion protein because at pH 6 (pH that is suboptimal for FDH), the dye reduction decreased to more than 50 % and this could be attributed to the impaired NADH supply for the AzoRo part