Mekelle Institute of Technology

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Subject: search.filters.subject.Biodegradation

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    Screening and Identification of Potential Dye-Degrading Bacteria from Maa Garment Effluen
    (Mekelle University, 2025-06-21) Berihu Zenawi
    The textile industry is a major contributor to water pollution, releasing effluents containing 10% - 15% unused dyes. These, dyes are resistant to biodegradation because their complex aromatic structures pose significant threats to aquatic ecosystems and human health. This study aimed to isolate, screen, and identify potential dye-degrading bacteria from the effluents of the Maa Garment and Textile Factory. Physicochemical parameters, including pH, temperature, total suspended solids (TSS), total dissolved solids (TDS), biological oxygen demand (BOD), and chemical oxygen demand (COD), were analyzed. Bacterial isolates were cultivated in dyecontaining media, and their decolorization efficiency was evaluated using spectrophotometry under varying conditions: temperatures (25°C, 30°C, 37°C, and 40°C), pH levels (5, 7, and 9), and dye concentrations (50, 100, and 150 mg/L). The collected samples exhibited pH levels ranging from 7.2 to 7.5 and the temperature varied significantly, with one sample reaching 38°C. A total of 16 bacterial isolates were screened for their decolorization capabilities under varying conditions of temperature, pH, and dye concentration. The results indicated that optimal decolorization occurred at 37°C and pH 7, particularly at a dye concentration of 50 mg/L. Under these conditions, the Pseudomonas aeruginosae isolates H5P, C2P, and C4P achieved 90% decolorization of reactive dyes. There were statistically significant differences (p < 0.001) among all environmental factors tested. These findings suggest that the isolated bacterial strains have considerable potential for the bioremediation of textile wastewater. This biological approach represents an environmentally sustainable and cost-effective alternative to conventional treatment methods. Further field trials and studies involving a broader range of dyes are recommended to validate their application in real-world wastewater treatment systems
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    Isolation and Characterization of Engine Oil-Degrading Bacteria from Contaminated Soil at Garage Centers in Mekelle
    (Mekelle University, 2025-06-20) Yohannes Tsegay Teklay
    The release of engine oil by Mekelle mechanical workshops causes significant environmental pollution; bioremediation is an effective cleanup strategy. This study investigates the isolation and characterization of engine oil-degrading bacteria from contaminated soil at garage centers in Mekelle. Soil and water samples from ten garage centers in Mekelle were collected and analyzed for physicochemical properties. Bacteria were isolated using serial dilution and identified by morphological and biochemical characteristics. To assess the oil degradation ability, bacterial isolates were cultured on Bushnell-Haas agar with engine oil and incubated at 37°C for 14 days. Moreover, the isolates were evaluated for biosurfactant production, heavy metals and salt tolerance, antibiotic susceptibility, as well as for compatibility. Results showed the pH level of the soil ranging from 4.7 ± 0.2 to 6.6 ± 0.2, with temperatures between 25 ± 3.27°C and 34 ± 0.0°C. The isolates were identified as Pseudomonas aeruginosa, Bacillus cereus, Staphylococcus aureus, Acinetobacter baumannii, Bacillus pumilus, and Bacillus megaterium. B. pumilus (98.9 ± 91.6%) showed the highest oil degradation rate in soil followed by A. baumannii (98.7 ± 80%). Whereas, B. megaterium (96.9 ± 92.8%), B. cereus (96.7 ± 88.2%), and P. aeruginosa (96.5 ± 84.6%) showed the highest biodegradation rate in water. However, B. megaterium (98.9 ± 88.8%) achieved a high degradation rate in media. The highest biosurfactant was produced by P. aeruginosa, A. baumannii, and B. cereus. S. aureus and A. baumannii exhibit broad tolerance to all tested heavy metals. P. aeruginosa, B. megaterium, B. cereus, and B. pumilus exhibit significant salt tolerance. Moreover, the antibiotic sensitivity testing reveals that P. aeruginosa, A. baumannii, and B. megaterium are promising candidates for bioremediation due to their susceptibility to effective antibiotics, while strains like B. cereus, S. aureus, and B. pumilus exhibit intermediate as well as multidrug resistance, necessitating careful antibiotic selection. So, from the results obtained, bacterial isolates could be the most effective for the bioremediation of oil spills.