ASTU ETD

Adama Science and Technology University Library Electronic Theses & Dissertations (ASTU- ETD) is a new digital institutional repository system that collects, preserve and distribute the scholarly output of the university, mainly postgraduate Electronic Thesis and Dissertation (ETD), articles, proceedings. The system is dedicated to help users to find all the information they might require in order to format and successfully submit their graduate thesis, dissertation and publications electronically. The user friendly web interface enables to maximize & optimize the resource sharing among ASTU different Colleges.

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Recent Submissions

Harnessing Chromogenic Bacteria for Eco-Friendly Textile Dyeing: Pigment Production and Process Optimization
(ASTU, 2026-01)
Birhanu Zeleke
Microbial pigments are emerging as sustainable alternatives to synthetic dyes due to their environmental compatibility and potential for circular bio-economy applications. This study focused on the identification of potent pigment-producing bacterial isolates, the use of agro waste substrates as low-cost substrates, and the optimization of culture parameters to enhance pigment yield. The study systematically explored pigment-producing bacterial isolates from environmental samples, employing morphological, biochemical, and MALDI-TOF analyses for identification. Eco-physiological tolerance was assessed using the one-variable-at-a-time approach, while culture optimization was conducted through Plackett–Burman Design followed by response surface methodology. Agro-waste extracts as low-cost substrates were evaluated via optical density measurements, and pigments were extracted using organic solvents. Pigments were characterized using UV-Vis spectroscopy, LC-MS, and ATR-FTIR. The pigments' stability under varying stressor conditions was assessed by monitoring absorbance at their characteristic wavelengths. Fabrics dyeing were conducted using immersion technique. Dye exhaustion and fixation to fabrics were evaluated via absorbance method after washing and exposure to sunlight. From purified colonies on streak plates, six isolates; namely: Acinetobacter sp., Exiguobacterium aurantiacum, two Kocuria spp. (from different samples), Micrococcus luteus, and one unidentified strain, exhibited chromogenic potential. Among the chromogenic isolates screened, Micrococcus luteus exhibited the highest pigment yield (1.47 g/L) under orange-waste extract cultivation, likely due to the isolate's inherent carotenoid biosynthetic capacity, stress tolerance, and efficient substrate utilization. Optimization of pigment production by Exiguobacterium aurantiacum using tomato-waste extract revealed that agitation rate, pH, and yeast extract concentrations were the most significant factors influencing culture growth (p<0.001), leading to 1.6-fold yield increment compared to un-optimized conditions. The characteristic UV-Visible absorbance peaks (400 550 nm) indicated the pigments are likely carotenoid compounds with functional group signatures (O–H, C–H, C=C, C=O) from infrared spectra analyses. The LC-MS analyses further resolved pigment mixtures, provided molecular weights and fragmentation patterns, indicating pigment heterogeneity. Stability assays of Micrococcus luteus pigment indicated susceptibility to oxidative and thermal stress, while dyeing trials demonstrated vibrant and uniform coloration with moderate fixation on fabrics. While microbial pigment production has been widely reported, existing studies predominantly rely on synthetic media. The present study is fundamentally novel, integrating systematic screening, agro-waste valorization, and multivariate statistical optimization, marking the first such effort in Ethiopia. The findings highlight Micrococcus luteus as a robust candidate for scalable, eco-friendly pigment production under low-cost sustainable culture conditions. The findings highlight the feasibility of low-cost, eco-friendly microbial pigments for industrial applications as promising alternatives to synthetic dyes.
Phytochemical screening, bioactive compound characterization and antimicrobial activity assay of Commelina benghalensis L. leaf
(ASTU, 2025-12)
Ayantu Hinsermu
C. benghalensis L., traditionally used for treating leprosy, fever, and snake bites. The study aimed to identify bioactive compounds, characterize essential oils, and evaluate the plant's potential as a source of therapeutic agents. Phytochemical screening was conducted on C. benghalensis leaves, followed by compound extraction. The antimicrobial activity of the leaf extract was assessed against selected human pathogens using the disc diffusion method. Antioxidant activity was evaluated using the DPPH assay. MIC, MBC, and MFC were determined using the Broth Dilution Method. The structure of the bioactive compound was determined using GC-MS, NMR and HPL. Data analysis was performed using non-parametric one-way ANOVA and Tukey's test. Methanol yielded the highest extract (23.54 g, 75.27%), followed by chloroform (5.11 g, 16.34%) and petroleum ether (2.62 g, 8.37%), reflecting the solvents' varying abilities to solubilize different phytochemicals. Qualitative phytochemical screening revealed the presence of alkaloids, tannins, flavonoids, steroids, terpenoids, saponins, phenols and coumarins aligned with the known diversity of bioactive compounds in C. benghalensis. GC-MS analysis of the essential oil identified 25 components, with five compounds as the major constituents, highlighting the potential for various applications based on these compounds' properties. Further isolation efforts using TLC and column chromatography led to the identification of 1,2-benzenedicarboxylic acid, 1,2-bis(2-ethylhexyl) ester (DEHP), a known plasticizer, confirming its presence in the plant extract. The extracts of C. benghalensis have demonstrated antibacterial activity against various bacterial strains, with inhibition zones ranged from 6±0.6 mm to 15.7±1.5 mm. The essential oil and methanol extracts were found to be the most effective. However, they have shown less effective than standard antibiotics. Furthermore, these extracts also exhibited antifungal activity against C. albicans, with inhibition zones from 8.7±1.2 mm to 16.7±3.1 mm, where the petroleum ether extract showed the highest activity. This comprehensive analysis underscores C. benghalensis's rich phytochemical profile and potential as a source of valuable bioactive compounds, warranting further investigation into its pharmacological and industrial applications.
Serological and Molecular Investigation of Coxiella burnetii Infection and Associated Risk Factors in Selected Sites of Ethiopian Livestock
(2025)
Ashenafi Milkesa
Coxiella burnetii (C. burnetii) infection is a significant global public health, veterinary, and economic concern. Despite the global public health and veterinary importance, information regarding its distribution, prevalence and risk factors is scarce in Ethiopia. Hence, a comprehensive sero-epidemiological and molecular investigation was conducted to characterize C. burnetii infection, the causative agent of Q fever, and its associated risk factors in livestock from Ethiopia. We carried out this study to bridge some of the knowledge and information gaps by focusing on the geographical distribution of serological evidence of infection in livestock slaughtered at major abattoirs in Addis Ababa, Adama, and Modjo, as well as pastoral areas of Oromia, Ethiopia. A total of 4,140 whole blood samples were collected from livestock species at three abattoirs (Addis Ababa, Adama, and Modjo) and three pastoral districts (Mega, Dubuluk, and Yabello) from January 2021 to May 2022. In addition, 264 biological samples consisting of milk, urine, vaginal swabs, aborted fetal tissues and whole blood were collected from livestock species in three pastoral districts (Moyale, Boku Luboma and Elweye) where there is evidence of reproductive problems. Moreover, 292 ticks were collected from infested livestock during the biological sample collection. During sample collection geographical data was collected using GPS for mapping the origin of livestock species sampled. Georeferencing was performed to accurately delineate the sample locations. The sera samples were analyzed for the presence of anti-C. burnetii antibodies using an indirect Enzyme Linked Immunosorbent Assay (iELISA) kit. Additionally, buffy coat from iELISA serum positive livestock, milk, urine, vaginal swabs, aborted fetal tissues, and ticks were analyzed by real time quantitative polymerase chain reaction (RT-qPCR) targeting cytochrome c oxidase subunit 1 (COX1) gene. Logistic regression analysis was used to quantify the association between seroprevalence of C. burnetii infection and various potential risk factors. Out of the 4,140 serum samples tested, 777 (18.77%; 95% CI: 17.59, 19.99) were found positive for C. burnetii antibody. The sero-prevalence estimate was 27.17% at Addis Ababa abattoir, 19.41% at Adama abattoir, 19.13% at Modjo abattoir and 12.1% in livestock tested from Mega, Dubuluk, Yabello pastoral areas. Sera analysis at the animal species level showed that cattle exhibited the lowest sero-prevalence estimate (11.83%; 95% CI, 10.27 13.53%), while the highest was observed in camels (28.39%; 95% CI, 25.16–31.80%). The sero-prevalence estimate was 21.34% (95% CI, 18.86–23.99%) in goats and 20.17% (95% CI, 17.49–23.07%) in sheep. Female livestock were observed to have a higher seroprevalence (26.65%; 95% CI, 23.37 30.13%) than male livestock (17.21%; 95% CI, 15.97–18.51%). The prevalence was also higher in adult livestock (25.02%; 95% CI, 23.26–26.85%) than their younger counterparts (11.03%; 95% CI, 9.64–12.54%). Higher seroprevalence of C. burnetii infection was also observed in livestock infested with ticks (carry ticks on their body parts) (80.99%; 95% CI, 73.55–87.08%) than those livestock which were not infested by ticks at all (7.05%; 95% CI, 6.52–7.59%). The results of multivariable logistic regression analysis showed that species, age, and tick infestation were important risk factors for C. xv burnetii infection. The odds of infection were 3.22 times higher in camels and almost twice as high in goats and sheep compared to cattle. Adult livestock were infected more likely (OR = 3.23) than young ones. Interestingly, a significant difference was observed in the sero prevalence of infection between livestock that were infested with ticks (OR = 16.32) and those which were tick-free. Furthermore, out of 384 buffy coat samples randomly selected from the iELISA sera positive livestock and tested by real-time quantitative PCR (RT-qPCR), none of them showed positive result. Similarly, none of the 264 biological samples (aborted fetal tissues, urine, milk, buffy coat, and vaginal swabs) tested by RT-qPCR showed positive result. The prevalence of tick infestation was highest in camels, with 143 ticks (49.0% of the total collection) while cattle had the lowest prevalence of infestation (23 ticks, 7.9%). The tick fauna was dominated by Rhipicephalus pulchellus (30.5%) and Amblyomma variegatum (15.4%), but Rhipicephalus pravus (1.0%) and Hyalomma truncatum (2.7%) being the least frequently observed tick species. Similar to the biological samples collected from livestock, all ticks (292) analyzed using RT-qPCR showed negative results. This suggests a potential low-level infection, intermittent pathogen shedding, or challenges with detection using the chosen gene target. In conclusion, this study provides the first comprehensive sero-epidemiological data for C. burnetii infection in a multi-species livestock population in Ethiopia, while also highlighting the challenge of molecular detection. The serological study revealed the widespread exposure of livestock to the C. burnetii (seropositive in the absence of vaccination), identified important risk factors, and warrants the need for enhanced surveillance and the implementation of biosecurity measures to safeguard both animal and public health.
Serological and Molecular Investigation of Coxiella burnetii Infection and Associated Risk Factors in Selected Sites of Ethiopian Livestock
(2025)
Ashenafi Milkesa
Coxiella burnetii (C. burnetii) infection is a significant global public health, veterinary, and economic concern. Despite the global public health and veterinary importance, information regarding its distribution, prevalence and risk factors is scarce in Ethiopia. Hence, a comprehensive sero-epidemiological and molecular investigation was conducted to characterize C. burnetii infection, the causative agent of Q fever, and its associated risk factors in livestock from Ethiopia. We carried out this study to bridge some of the knowledge and information gaps by focusing on the geographical distribution of serological evidence of infection in livestock slaughtered at major abattoirs in Addis Ababa, Adama, and Modjo, as well as pastoral areas of Oromia, Ethiopia. A total of 4,140 whole blood samples were collected from livestock species at three abattoirs (Addis Ababa, Adama, and Modjo) and three pastoral districts (Mega, Dubuluk, and Yabello) from January 2021 to May 2022. In addition, 264 biological samples consisting of milk, urine, vaginal swabs, aborted fetal tissues and whole blood were collected from livestock species in three pastoral districts (Moyale, Boku Luboma and Elweye) where there is evidence of reproductive problems. Moreover, 292 ticks were collected from infested livestock during the biological sample collection. During sample collection geographical data was collected using GPS for mapping the origin of livestock species sampled. Georeferencing was performed to accurately delineate the sample locations. The sera samples were analyzed for the presence of anti-C. burnetii antibodies using an indirect Enzyme Linked Immunosorbent Assay (iELISA) kit. Additionally, buffy coat from iELISA serum positive livestock, milk, urine, vaginal swabs, aborted fetal tissues, and ticks were analyzed by real time quantitative polymerase chain reaction (RT-qPCR) targeting cytochrome c oxidase subunit 1 (COX1) gene. Logistic regression analysis was used to quantify the association between seroprevalence of C. burnetii infection and various potential risk factors. Out of the 4,140 serum samples tested, 777 (18.77%; 95% CI: 17.59, 19.99) were found positive for C. burnetii antibody. The sero-prevalence estimate was 27.17% at Addis Ababa abattoir, 19.41% at Adama abattoir, 19.13% at Modjo abattoir and 12.1% in livestock tested from Mega, Dubuluk, Yabello pastoral areas. Sera analysis at the animal species level showed that cattle exhibited the lowest sero-prevalence estimate (11.83%; 95% CI, 10.27 13.53%), while the highest was observed in camels (28.39%; 95% CI, 25.16–31.80%). The sero-prevalence estimate was 21.34% (95% CI, 18.86–23.99%) in goats and 20.17% (95% CI, 17.49–23.07%) in sheep. Female livestock were observed to have a higher seroprevalence (26.65%; 95% CI, 23.37 30.13%) than male livestock (17.21%; 95% CI, 15.97–18.51%). The prevalence was also higher in adult livestock (25.02%; 95% CI, 23.26–26.85%) than their younger counterparts (11.03%; 95% CI, 9.64–12.54%). Higher seroprevalence of C. burnetii infection was also observed in livestock infested with ticks (carry ticks on their body parts) (80.99%; 95% CI, 73.55–87.08%) than those livestock which were not infested by ticks at all (7.05%; 95% CI, 6.52–7.59%). The results of multivariable logistic regression analysis showed that species, age, and tick infestation were important risk factors for C. xv burnetii infection. The odds of infection were 3.22 times higher in camels and almost twice as high in goats and sheep compared to cattle. Adult livestock were infected more likely (OR = 3.23) than young ones. Interestingly, a significant difference was observed in the sero prevalence of infection between livestock that were infested with ticks (OR = 16.32) and those which were tick-free. Furthermore, out of 384 buffy coat samples randomly selected from the iELISA sera positive livestock and tested by real-time quantitative PCR (RT-qPCR), none of them showed positive result. Similarly, none of the 264 biological samples (aborted fetal tissues, urine, milk, buffy coat, and vaginal swabs) tested by RT-qPCR showed positive result. The prevalence of tick infestation was highest in camels, with 143 ticks (49.0% of the total collection) while cattle had the lowest prevalence of infestation (23 ticks, 7.9%). The tick fauna was dominated by Rhipicephalus pulchellus (30.5%) and Amblyomma variegatum (15.4%), but Rhipicephalus pravus (1.0%) and Hyalomma truncatum (2.7%) being the least frequently observed tick species. Similar to the biological samples collected from livestock, all ticks (292) analyzed using RT-qPCR showed negative results. This suggests a potential low-level infection, intermittent pathogen shedding, or challenges with detection using the chosen gene target. In conclusion, this study provides the first comprehensive sero-epidemiological data for C. burnetii infection in a multi-species livestock population in Ethiopia, while also highlighting the challenge of molecular detection. The serological study revealed the widespread exposure of livestock to the C. burnetii (seropositive in the absence of vaccination), identified important risk factors, and warrants the need for enhanced surveillance and the implementation of biosecurity measures to safeguard both animal and public health.
Bioremediation Potential and Molecular Characterization of Heavy Metal-resistance Profiles of Bacterial Isolates from Industrial Effluents in Mojo and Bishoftu area, Ethiopia
(2025)
Duguma Dibbisa
;
Tadessa Daba (PhD)
;
Seid Mohammed (PhD)
Various heavy metals (HM) can be removed from the environment by various bacterial species, which are developing resistance and reduction through various mechanisms. Bacteria bioaccumulate Heavy metals (HMs) inside their cell structures. This study aimed to isolate and characterize heavy metal–resistant bacterial isolates (HMRBI) from environmental samples collected in Ethiopia’s Bishoftu Eastern Industrial Zone and Mojo Tannery Industry, with the objective of mitigating environmental pollution. Soil and wastewater samples were collected and transported to the Molecular biology and Biotechnology laboratory, Haramaya University. The HMRBIs were subsequently screened and identified based on their resistance to selected heavy metals. These isolates were characterized and identified using biochemical assays, protein profiling through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and molecular analysis based on 16S rRNA gene sequencing. Furthermore, several computational approaches were employed to investigate the expression patterns and regulatory mechanisms of heavy metal resistance genes (HMRG). These included comparative genomes, predicting promoter regions, & common sequence motifs, identifying transcriptional sites, re-annotating genes, and identifying transcriptional factors. The Multiple Em Motif FOR Elicitation (MEME Suite), Rapid Annotation using Subsystem Technology (RAST), Orthologous Average Nucleotide Identity (OANI), and EziBIO databases were key tools utilized in this analysis. Cell deformation, bio-absorption, and infrared spectra corresponding to heavy metal uptake by cells were examined using scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) and Fourier transform infrared spectroscopy (FTIR). Atomic Absorption Spectrophotometry (AAS) was also utilized to assess the biodegradability of HMRBI. Among seventeen characterized bacterial isolates, Pseudomonas putida-HMRBI-2 showed the highest ability to bioaccumulate cobalt, with removal rates of 67.38%. Exiguobacterium aurantiacum strain HMRBI-7 was the most effective at removing copper and chromium, with bioaccumulation rates of 65.02 ± 0.002% and 70.04 ± 0.001%, respectively. Aeromonas hydrophila strain HMRBI-12 and Delftia acidovorans-HMRBI strain 7 demonstrated good cadmium and zinc removal abilities, with bioaccumulation rates of 65.02% and 70.32%, respectively. Although each bacterial isolate exhibited variable levels of HM resistance, they all showed unique capabilities for the bioaccumulation of HMs. It is believed that the isolate most likely possesses a combination of intracellular and extracellular biosorption mechanisms to degrade HMs. The study, which utilized xvieight 16 rRNA gene sequences, successfully identified three microbial isolates: P. benzoelyticum strain HMRBI-1, Citrobacter strain HMRBI-5, and Klebsiella strain HMRBI-14 as having the highest HM removal capacity. Furthermore, the minimum inhibitory concentration (MIC) results highlighted that Klebsiella spp. exhibited an MIC of 700 ppm, whereas Citrobacter spp. presented an MIC of 800 ppm. Moreover, the maximum bioaccumulation efficiencies were noted at 89.74, 85.21, and 79.27% for Klebsiella strain HMRBI-14, Citrobacter strain HMRBI-5, and P. benzoelyticum strain HMRBI-1, respectively. Additionally, 14 transcription factors were identified and predicted from the reliable and lowest candidate motif with an e-value of 3.0e-009. Further investigation was conducted on the 14 identified transcription factors concerning activation, repression, and dual functions and regulation in microorganisms to thrive in harsh environmental conditions. As the data suggest, the identified transcription factors were used for the activation of gene regulation rather than repression. Therefore, the study highlights the importance of bacteria in HM bioremediation at contaminated sites due to the genes they possess. Analyzing regulatory elements provides a crucial foundation for understanding the genes the key to HM bioremediation, and the combined approach of laboratory experiments and bioinformatics effectively harnesses native microorganisms to clean heavy metal-contaminated environments.