Mekelle Institute of Technology
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Item Isolation and Characterization of Engine Oil-Degrading Bacteria from Contaminated Soil at Garage Centers in Mekelle(Mekelle University, 2025-06-20) Yohannes Tsegay TeklayThe 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.Item Evaluation of Aframomum corrorima Seed Extracts and Their Green Synthesized Silver Nanoparticles for Their Antioxidant, Antibacterial, and Wound Healing Activities(Mekelle University, 2025-04-28) Rahel Sisay WeredeThe emergence and spread of multidrug-resistant bacteria pose a significant medical challenge today. This research aimed to evaluate the antioxidant, antibacterial, and wound-healing activities of Aframomum corrorima seed extracts and their green-synthesized silver nanoparticles (AgNPs). Seeds of A. corrorima, collected from Hawassa, were ground into powder, macerated with ethanol, methanol, and water, and extracted using the Soxhlet extraction method. The qualitative phytochemical profile of the A. corrorima seed extracts was evaluated. AgNPs were synthesized from the A. corrorima extracts, and their properties were analyzed using UV-Vis and FTIR spectroscopies, Scanning electron microscopy, and X-ray diffraction. The three extracts and the AgNPs were tested against E. coli, P. aeruginosa, and S. aureus. The wound-healing potential of the extracts, formulations, and the AgNPs was evaluated using a mice model. The antioxidant capacities of the seeds and AgNPs were also assessed. Phytochemical analysis revealed flavonoids, tannins, glycosides, phenols, saponins, and quinones, with no detectable proteins. The methanol extract showed the highest antioxidant activity (IC50 23.38 ± 0.86 mg/ml), but AgNPs exhibited significantly greater potency (IC50 4.41 ± 0.025 mg/ml). AgNPs characterization confirmed nanoscale synthesis. Antibacterial assays demonstrated that AgNPs, seed extracts, and their formulations effectively inhibited E. coli, S. aureus, and P. aeruginosa, surpassing controls. AgNPs were most effective against S. aureus, and synergistic combinations enhanced antibacterial activity. Toxicity tests confirmed the safety of extracts and AgNPs in mice. Wound-healing studies in mice showed that seed extract, AgNPs, and their formulation significantly accelerated wound contraction compared to controls and nitrofurazone. The formulation improved healing by 11% over standard ointment. AgNPs and extracts displayed wound-healing comparable to nitrofurazone. This research highlights the potential of A. corrorima seed extracts and AgNPs as safe and effective sources of antioxidants, antibacterial agents, and wound-healing therapeutics, offering alternatives for multidrug- resistant bacterial infections and wound management.Item Isolation and characterization of Lactic Acid Bacteria from raw cow milk and evaluation of their probiotic potential(Mekelle University, 2025-04-28) Goiteom Senay NiguseCow milk is a rich source of lactic acid bacteria (LAB), a group of gram-positive bacteria with diverse applications in dairy, food, feed, and health. Despite this, the probiotic potential of LAB from cow milk remains under-researched. Therefore, the current study aimed to isolate and characterize LAB from raw cow milk and evaluate their probiotic potential. This study involved the isolation of LAB, followed by characterization of their morphology, various biochemical tests, and physiological properties. The LABs were evaluated for their potency and safety as probiotics, and finally, their potential use as starter cultures in yogurt formation was examined. Twenty-three (23) pure bacterial isolates were obtained from seven cow milk samples. Morphologically, eight isolates were cocci (35%), six were rods or bacilli (26%), and nine were coccobacilli (39%). Among these, nine (9) gram-positive and catalase negative isolates were selected for further investigation. These isolates were citrate-negative, non-motile, and indole- negative. All were TSIA-positive, with seven being homo-fermentative and two (M5 and M9) hetero-fermentative. Isolates M1, M2, M3, M4, M5, M6, M7, and M9 demonstrated salt tolerance at 1%, 4%, and 6% NaCl concentrations. Isolates M3 and M4 exhibited acid tolerance, growing at pH levels of 2, 4, 6, and 6.5. Isolates M1, M2, M3, M5, M6, M7, and M9 showed resistance to temperatures ranging from 15°C to 45°C. Isolates M2, M3, M5, M6, M7, M8, and M9 displayed tolerance to 0.4% and 0.6% phenol concentrations. None of the nine LAB isolates exhibited hemolytic activity. However, they showed varying degrees of antibacterial activity and displayed both susceptibility and resistance to antibiotics. Six isolates (67%) performed well as starter cultures for yogurt (riguo) production. The LAB isolates were tentatively grouped under the genera Lactobacillus, Enterococcus, and Leuconostoc. Overall, the isolated LAB from cow milk represents a potential source of probiotics. These LABs could serve as starter cultures in the dairy and food industries and may be developed into commercially viable probiotic products. Further studies, including molecular identification and characterization, are necessary to determine their specific strains.Collection Collection