ORIGINAL RESEARCH
Optimization of Azo Dyes Removal by Several Eco-
Friendly Bacterial Isolates from Textile Wastewater
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1
Agriculture Microbiology Department, National Research Centre, Dokki, 12622, Giza, Egypt
2
College of Biotechnology, Misr University for Science and Technology (MUST), Giza 12588, Egypt
3
Center for Health Research, Northern Border University, Arar 73213, Saudi Arabia
4
Biotechnology Institute, University of Minnesota, Minnesota 55108, USA
5
College of Biosystems Engineering and Food Science, Zhejiang University,
866 Yuhangtang Road, Hangzhou, 310058, China
6
Department of Nutrition & Food Science, National Research Centre, Dokki, 12622, Giza, Egypt
Submission date: 2025-04-24
Final revision date: 2025-06-24
Acceptance date: 2025-07-14
Online publication date: 2025-10-13
Corresponding author
Wafaa M. Abd El-Rahim
Agriculture Microbiology Department, National Research Centre, Dokki, 12622, Giza, Egypt
Eman R. Elsharkawy
Center for Health Research, Northern Border University, Arar 73213, Saudi Arabia
Mostafa M. Gouda
College of Biosystems Engineering and Food Science, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China, China
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ABSTRACT
Industrial effluents from the textile industry often contain recalcitrant azo dyes that pose severe
environmental and public health risks. This study aimed to isolate and identify bacterial strains
capable of biodegrading various azo dyes and to optimize environmental conditions for enhanced
decolorization. Twelve bacterial isolates were obtained from different environments and identified
using 16S rRNA sequencing. The capability of these bacteria to decolorize 20 distinct azo dyes
was assessed in a mineral salt medium (MSM), where textile methyl red (TMR) and textile direct
violet (TDV) azo dyes served as the primary carbon sources. The results showed that B. brevis, B.
coagulans, L. macrolides, L. fusiformis, and B. subtilis species significantly degraded 20 diverse azo
dyes in MSM, with Bacillus coagulans and Lysinibacillus macrolides achieving decolorization rates
of 88.7% and 82.6%, respectively. Additionally, we optimized key growth factors, including glucose,
nitrogen source, and microelement concentrations, which significantly influenced enzyme production
and biomass accumulation. Enzyme assays demonstrated the activity of lignin peroxidase, laccase, and
azoreductase under different nutrient conditions. The decolorization efficiencies varied with substrate
type and bacterial strain, revealing unique enzymatic responses. Where B. coagulans and L. macrolides
were the best isolates (p<0.01) for the biodegradation process of azo dyes. In conclusion, these study
findings provide insights into sustainable and eco-friendly wastewater remediation strategies utilizing
indigenous bacterial strains with high biodegradation potential.