Streptomyces as a Novel Biotool for Azo Pigments Remediation in Contaminated Scenarios.

Background: Azo pigments are widely used in the textile and leather industry, and they generate diverse contaminants (mainly in wastewater effluents) that affect biological systems, the rhizosphere community, and the natural activities of certain species.

Methods: This review was performed according to the Systematic Reviews and Meta Analyses (PRISMA) methodology.

Results: In the last decade, the use of Streptomyces species as biological azo-degraders has increased, and these bacteria are mainly isolated from mangroves, dye-contaminated soil, and marine sediments. Azo pigments such as acid orange, indigo carmine, Congo red, and Evans blue are the most studied compounds for degradation, and Streptomyces produces extracellular enzymes such as peroxidase, laccase, and azo reductase. These enzymes cleave the molecule through asymmetric cleavage, followed by oxidative cleavage, desulfonation, deamination, and demethylation. Typically, some lignin-derived and phenolic compounds are used as mediators to improve enzyme activity. The degradation process generates diverse compounds, the majority of which are toxic to human cells and, in some cases, can improve the germination process in some horticulture plants.

Conclusions: Future research should include analytical methods to detect all of the molecules that are generated in degradation processes to determine the involved reactions. Moreover, future studies should delve into consortium studies to improve degradation efficiency and observe the relationship between microorganisms to generate scale-up biotechnological applications in the wastewater treatment industry.