Browsing by Author "Assefa Fassil (PhD)"

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    Antagonistic and Antibiotic Effects of Endophytic and Rhizobacteria of Sugarcane Plant at Wonji Sugar Estate, Ethiopia
    (Addis Ababa University, 2013-06-06) Tilahun Sefinew; Lakew Mekuria (PhD); Assefa Fassil (PhD)
    The thesis targeted to identify the endophytic, (leaf and root) and rhizobacteria of three sugarcane sample plants taken from different sites of Wonji sugar estates plantation. Accordingly, leaf and root samples cleared of surface bacteria by chemical sterilization, crushed using sterile mortar and pestle and the extract plated on nutrient agar media. The soil samples were also sieved and serially diluted from 10-1 -10-6 and 100µl of the solution spread plated on nutrient agar media. A total of 40 representative isolates were identified based on standard morphological characterization. These isolates were sub cultured for purity and preserved on nutrient agar slant for future use in different testes: Antagonism, Antibiotic effect and development of serological methods of screening of the isolates. The identification of the isolates was done in two steps. First, grouping of the isolates by morphological, physiological and Biochemical tests and second, sorting of the groups that had more than one genera in to the specific genus was done by Busnson’s method. The result showed 11 genera, the dominant of which were Shigella, Bacillus and Klebsiella. Antagonstic interactions between all the isolates revealed 22 of them were susceptible to 18 isolates that had inhibitory effects. The test for antibiotic effect of isolates against four human pathogenic bacteria: E. coli, Salmonella thyphimurium, Staphylococcus aureus and Streptococcus pneumonae showed 18 isolates with anti-biotic effects ranging from 10-17mm clear zone diameter. This was less sensitive compared to the positive control antibiotics, chloranphenicol and ampicillin. The serological method development for screening of the isolates was started by SDS-PAGE fractionation of the proteins and induction of antibodies in swiss albino mice shall be tested as soon as the conjugated antibodies arrive. The potential use of the identified isolates; in sustainable agriculture, environmental protection and animal and human benefits are discussed in detail.
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    Arbuscular Mycorrhizal Fungal diversity of Coffee and Shade trees of Bonga forest, South Western Ethiopia.
    (Addis Ababa Universty, 2006-07) Chanie Tadesse; Assefa Fassil (PhD)
    To date, information regarding densities and identification of dominant coffee shade trees and explanation of their interaction with physical parameters in southwestern part of Ethiopia is extremely very scanty. Moreover, mycorrhizal fungi spore densities, colonization rate, diversity and interaction with physical and chemical parameters of soil are not evaluated in any of the coffee forest in the country and this work is to bridge such information gap. So, reconnaissance survey was conducted and the number of coffee and coffee shade tree species was counted with in a 20m x 20 m quadrat. Spores were separated from the bulk of the soil by the wet sieving and decanting method followed by sucrose centrifugation and counted per 100 g dry soil. Percent root colonization was determined clearing the root segments in 10 % KOH and stained with 0.05 % trypan blue.During the reconnaissance survey extremely large number of coffee seedlings and saplings were observed in the study area. Olea capensis, Schefflera abyssinica, Phoenix reclinata and Prunus africana were encountered as dominant shade tree species with percentage occurrences of 15, 12, 11 and 10 %, respectively. Milletia ferruginea, Albizia gummifera, Cordia africana, Croton macrostachyus and Dracaena steudneri comprise 40 % of the total number of plant species. Twenty four percent of the dominant shade trees were principally represented by leguminous trees such as M. ferruginea and A. gummifera. Arbuscular mycorrhizal fungal status was also investigated. Investigation of roots and rhizosphere soils of 14 shade tree species, M. ferruginea, S. abyssinica, C. macrostachyus, Ficus vasta, A. gummifera, O. capensis, C. africana, Ehretia abyssinica, Pouteria adolfi-friederici, Pavetta oliveriana, Ficus sur, P. africana, P. reclinata and Polyscias fulva, and the coffee tree underneath revealed arbuscular mycorrhizal colonization and different types of AM spores. The number and morphological type of spores were determined in 100g of rhizosphere soil. All species had a high level of AM colonization. F. vasta, C. macrostachyus, S. abyssinica and O. capensis spp. had the highest level of colonization. E. abyssinica, P. africana and P. fulva exhibited the lowest level of colonization. The coffee trees revealed generally maximum colonization than respected shade trees. The number of spores forming AM in all rhizosphere soils ranged between 578-1313 spores/ 100g of dry soil. Spores were grouped in four principal morphological types Glomus, Gigaspora, Scuttelospora and Acaulospora in descending order of relative abundance, respectively. Spore density and colonization percentage were found to be negatively correlated with O.C, total N, available P, EC and Zn. Population of spore types were also some how determined by soil physical and chemical properties. Arbuscular Mycorrhizal fungi are commonly considered to be non specific with respect to their host and their ability to colonize particular plant species. Conversely, it is investigated that plant species differ in their ability to form and benefit from mycorrhizal relationship. This study didn’t investigate the whole range of organisms in the rhizosphere which could give benefits to trees. So, it is difficult to draw conclusion that the well being of the shade trees and coffee plants in the natural forest is due to only AMF colonization. However, AMF could be considered to be a future tool in agriculture, i.e. fertilizer substitute and as biocontrol agent. So, it is recommended that: (a) studying the ecology, diversity and host range of AMF is of enormous importance before application. (b) their relation with nutrient dynamics and other soil characteristics should be evaluated before use. (c) these organisms should receive the proper management. (d) the impact of litter fall on AMF spore density and diversity should be evaluated in the future. Finally, this symbiosis command great interest as the subject of future research with relation to food security
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    Assessment of Biological Integrity Using Physico-Chemical Parameters and Macroinvertebrate Community Index Along Sebeta River, Ethiopia
    (Addis Ababa University, 2007-07) Tassew Admasu; Assefa Fassil (PhD); Mengistuo Seyoum (PhD)
    The level of water pollution and ecological disturbance of Sebeta River was evaluated using some important physico-chemical and biological parameters. The Physico-chemical parameters were: flow velocity (m/s), dissolved oxygen (DO) (mg/L), pH, temperature (0c), electrical conductivity (EC) (μs/cm), nitrate-nitrogen (mg/L) and phosphate (mg/L). The mean flow velocity and nitrate-nitrogen measures showed no significant difference between the study sites of Sebeta River (P > 0.05). DO records of the river at the upstream rural sites above Sebeta Agro-industry (SR1 and SR2) were significantly higher than the DO records of the downstream sites (P < 0.001). The mean pH values of SR3 (3.60 ± 0.81) (immediately downstream from Bale Zaf Alcohol and Liquor Factory and Soap Factory) and SR4 (4.75 ± 0.88) (downstream of National Alcohol and Liquor Factory and Blue Nile Tannery) were significantly lower than the pH values of the rest of the sample sites (P < 0.001). The mean temperature and EC records of SR3 (33.83 ± 1.17 0c, 16050.00 ± 2270.77 μs/cm) and SR4 (27.63 ± 0.68 0c, 15400.00 ± 316.60 μs/cm) were significantly higher than the respective records at the rest of the study sites (P < 0.001). Phosphate concentration at SR3 (8.59 ± 1.16 mg/L) was significantly higher than the phosphate concentrations recorded from the other sites (P < 0.001). Flow velocity and nitrate-nitrogen of Sebeta River were in the natural range, except for extreme values at sites SR3 and SR4. Habitat integrity assessment was done according to the US Environmental Protection Agency Rapid Bioassessment Protocol. Percent comparability of habitat scores classified the upstream reference sites to good, while it categorized the entire downstream sites to very poor. The mean chlorophyll ‘a’ measures of upstream reference sites (SR1 and SR2) showed significantly higher values than those of the impacted downstream sites (P < 0.001). Macroinvertebrate community index of Sebeta River (MCISR) was developed using selected metrics. The MCISR score classified both of the upstream sites (SR1 and SR2) to very good biological integrity, while it classified all the downsteam sites to very poor biological integrity, but SR8 (further down in Atebela peasants association) to poor.
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    The Assessment of Microbial-Safety of Fruit Juices Consumed In Cafes and Restaurants of Humera Town, Western Tigray Ethiopia
    (Addis Ababa University, 2017-08-03) Berhe Haddis; Assefa Fassil (PhD)
    Freshly squeezed fruit juices are very important for human being which contributes vital nutrients especially Vitamin C. However, unpasteurized juices which are contaminated during processing from raw materials, poor hygienic conditions, using of tap water for all processing and unsafe environmental conditions of juice processing resulting in different food- borne illnesses. The study was aimed to assess bacteriological load of fruit juices served in cafes and restaurants of Humera Town. A cross sectional study was conducted from October 2009 to February 2009 in Humera Town. A total of 24 sample juices eight of each Avocado, Mango and Papaya were collected from five randomly selected cafes and restaurants of Humera town and analyzed their bacteriological quality. The samples were correctly serially diluted and incubated on proper temperature and selected nutrient Agar to determine bacterial load. Streak and pour plate method was used for the growth of bacteria on the selective media. The Total microbial load of Avocado juice was determined as 12.71x107cfu/ml and the Total mean was determined as 2.54x107cfu/ml, the Total microbial load of Mango juice was determined 11.54x107cfu/ml with Total mean of microbial load 2.31x107cfu/ml and the Total microbial load of Papaya juice was determined as 10.93x107cfu/ml with Total mean of 2.18x107cfu/ml. Well structured questionnaire was conducted to analyze hygienic conditions of juice makers, awareness of contaminations of juice makers, storage sites of fruits, sources of fruits, safety of water and hygienic of juice processing conditions. The reason for high microbial load of samples of fruit juices were due to poor personal hygiene, use of contaminated water for all processing, unhygienic environmental conditions and lack of knowledge and training in food hygiene and safety. Therefore special training and supervision of juice makers how to handled and processing juices in hygienic and safely conditions were improved the quality of fruit juices vended in the streets.
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    Assessment of Physicochemical and Bacteriological Quality of Drinking Water Supply from Different Boreholes of Addis Ababa
    (Addis Ababa University, 2018-02-02) Negash Hiluf; Assefa Fassil (PhD)
    Assessment of physicochemical and bacteriological quality of drinking water is important to protect public health. Little is known about the quality of drinking water in Addis Ababa. Therefore, this study was aimed to assess the physicochemical and bacteriological quality of drinking water in different sites of Addis Ababa and determine whether the drinking water quality meet the national standards and WHO criteria guideline values for drinking water quality standards. A total of 180 water samples were collected and analyzed in triplicate sampling from selected 20 boreholes. The mean physicochemical and bacteriological quality of each method were calculated and compared with the set standards of WHO and National standards. The mean physical parameters of the boreholes were ranging from pH (6.6±.5) Ararat to(7.7±.7) Yeka borehole in Northern Addis Ababa; temperature 21.8±.6°C Alemgena Southern Addis Ababa to 26.4±1.02°C BH6 in Central Addis Ababa; TDS 230±3.5mg/l Alemgena to 308±12.2mg/l Mekanisa197 borehole in Southern Addis Ababa; EC 458.7±5.6µS/cm Alemgena in Southern Addis Ababa to 639.3±31.7µS/cm BH24 in central Addis Ababa; turbidity 0±0 to 0.13±0.08NTU. And the physical parameters of the sites were ranging from pH 7.1±.3 in Central and Southern Addis Ababa to 7.1±.8 in Norther Addis Ababa; temperature 23.8±.8°C in Southetn Addis Ababa to 24.8±.8°C in Northern Addis Ababa; TDS 247.1±.15mg/l in Southern Addis Ababa to 271.4±9.1mg/l in Northern Addis Ababa; EC 534.8±29.8µS/cm Southern Addis Ababa to 543±9.1µS/cm in Northern Addis Ababa and turbidity 0.01±.01NTU in Northern and Southern Addis Ababa to 0.02±.01NTU in Central Addis Ababa. The mean chemical parameters recorded of the boreholes were ranging for nitrate 3.5±.7 mg/l Selam to 33.9±1.8mg/l Ankorcha2 boreholes in Northern Addis Ababa; DO 4±1.2mg/l Mekanisa296 borehole in Southern Addis Ababa to 8.9±.2mg/l BH24 in Central Addis Ababa and BOD 0.21±.11 mg/l Selam borehole in Northern Addis Ababa to 3.±.11mg/l BH14 in Central Addis Ababa; which were above the WHO limit. Moreover the mean Fluoride values ranges from 0.55±.03mg/l Ararat borehole in Northen Addis Ababa to 0.98±.01mg/l BH19 in Central Addis Ababa all boreholes below WHO limit for domestic water use. Whereas, the mean chemical parameters of the sites were ranging from nitrate 10±.8mg/l in Southern to 25.6±1.8mg/l in Central Addis Ababa; DO 6.4±.6mg/l in Southern Addis Ababa to 7.3±.5mg/l in Northern Addis Ababa and BOD 0.98±.32mg/l in Central Addis Ababa and 1.2±.33mg/l in Southern Addis Ababa. In addition the mean average fluoride 0.67±.04mg/l in Northern Addis Ababa to 0.69±.06mg/l in Southern Addis Ababa. The mean bacteriological counts of the boreholes were ranging from 26±1.5CUF/100ml to 217.3±5.8CFU/100ml; 20±7.6CFU/100ml to 75±2.1CFU/100ml, and 0±.0CFU/100ml to 23±2.9 CFU/100ml for TC, FC and FS respectively. The mean of the sites were range from 73.6±34.6 CFU/100ml in central Addis Ababa to 39±8.2CFU/100ml in southern Addis Ababa for TC; 28±7.2CFU/100ml in Southern Addis Ababa to 46±6.6CFU/100ml in Northern Addis Ababa for FC and 8±1.1CFU/100ml in Southern Addis Ababa to 13±1.9CFU/100ml in Northen Addis Ababa for FS. Inwhich both were above the permissible limit of WHO and national standards except Alemgena borehole in Southern Addis Ababa (FS=0±.0CFU/100ml) which comply with the WHO criteria and national standards. The bacteriological quality and temperature of most of the boreholes and all of the sites did not meet ES and WHO standards.
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    Bioethanol Production from Lignocellulose, Whey and Starch Using Yeasts Isolated from Ethiopian Traditional Beverage and Other Sources
    (Addis Ababa University, 2018-05-04) Tesfaw Asmamaw; Assefa Fassil (PhD)
    Ethanol is produced by yeasts and used for different applications. The ever-increasing demand for energy necessitates the production of ethanol as biofuel to supplement fossil fuels as a source of energy and protect the environment from environmental pollution. This requires for selection of effective ethanol producing local yeasts to produce ethanol from easily available agricultural wastes. To this end, indigenous yeasts were isolated from yeast habitats such as traditional fermented beverages, soil, flower, and compost samples collected from different part of Ethiopia. The isolates were screened for their glucose fermentation and ethanol production.. The selected yeast isolates with better ethanol production from glucose were identified using 26S rRNA sequence analysis using NL1 and NL4 primers. They were further evaluated for their ability to ferment different carbon sources, sedimentation rate, tolerance to sugar and ethanol concentration. Production of ethanol by selected yeasts was optimized based on variables such as inoculum size, temperature, pH, and incubation time using response surface methodology based on central composite design. Enzymatic, acid, and alkali hydrolysis, and coculture were employed to produce ethanol from grass pea and wild oat straws and starch. In order to produce ethanol from whey, experimental runs such as molasses and external nutrient supplementation, effect of whey pH, sterilized and non-sterilized whey were evaluated. Five isolates were identified as Saccharomyces cerevisae and the remaining three were grouped into Kluveromyces marxianus, Pichia fermentans and Candida humilis. The pattern of sugar utilization showed that only K. marxianus ETP87 and P. fermentans ETP22 were able to grow on xylose; and K. marxianus ETP87 was the only yeast that fermented lactose and, therefore, was selected to produce ethanol from whey. All the 8 yeasts other than C. humilis were able to flocculate a feature that makes the biomass separation easy for industrial applications. Regarding tolerance to ethanol, S. cerevisae ETP53, K. marxianus ETP87, P. fermentans ETP22 and C. humilis ETP122 were tolerant to 10% extraneous ethanol but the percentage of ethanol tolerance considerably decreased at 15% and 20% ethanol shock treatment. S. cerevisae ETP53 produced ethanol optimally at pH 5.0, 60 hours, and 34oC; whereas the optimal growth and fermentation by K marxianus ETP87 was at pH 4.8, temperature 36oC, and incubation time of 65 hours. Highest reducing sugar was released from 1% (v/v) H2SO4 and 1% (w/v) NaOH treated straws; where sulfuric acid yielded higher amount of sugars than NaOH, and more ethanol was obtained from alkali hydrolysates. Significant amount of furfural was liberated from acid hydrolyzed straw that was reduced by treatment with activated carbon and overliming. The data also showed that significant amount of sugars was released from fungi (Pleurotus ostreatus M2191, Pleurotus sajor-caju M2145, Trichoderma reesei JCM22676, and Aspergillus niger JCM22344) grown on straws solid state media than enzymatic and chemically treated straws. However, the ethanol xiv production from fungal-treated straws was small. It was also established that higher ethanol production was obtained from acid-hydrolyzed sorghum flour than the one produced from crude amylase enzyme treated substrate and ethanol derived from coculturing, indicating that simultaneous saccharification and fermentation is a promising method to produce ethanol from starch. The data also showed that K. marxianus ETP87 was capable of producing ethanol from non-sterilized and non-deproteinized substrates. The effect of nutrient supplementation to whey was variable depending on the kind of nutrient added. Generally, it could be concluded that S. cerevisiae ETP53, K. marxianus ETP87, and P. fermentans ETP22 are promising yeasts to produce ethanol from different substrates at acidic pH, near 35oC and late fermentation time.
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    Characterization of Aspartic Protease Enzyme from Fungi and Bacteria and Its Potential Application for Cheese Production
    (Addis Ababa University, 2020-01-01) Mamo Jermen; Assefa Fassil (PhD)
    Cheese is a dairy product processed through milk clotting using rennet enzyme (chymosin) (EC 3.4.23.4). Chymosin is a complex enzyme produced by animals, plants or microorganisms. Traditionally, it is extracted from the fourth stomach (abomasum) of young ruminants. However, only 20-30% of the world demand for milk-clotting enzymes is covered by calf rennet, indicating that the milk-clotting enzymes derived from animals are not sufficient to cover worldwide cheese production. This necessitates the search for alternative sources for calf rennet substitutes such as microbial aspartic proteases. In this study, a total of 237 (188 fungal and 49 bacterial) isolates were tested for milk-clotting enzyme production in primary and secondary screening techniques. After the secondary screening, 17 potential fungal and 14 bacterial isolates were successfully identified using, a combination of phenotypic and molecular techniques. The physicochemical parameter and media composition for potential fungus (Aspergillus oryzae DRDFS13) under SSF were optimized by one-factor-at-a-time and Response Surface Methodology (RSM) whereas the culture profile of the potential bacterium (Bacillus subtilis SMDFS 2B) was studied under partially optimized conditions. The enzyme from A. oryzae DRDFS13 was characterized molecularly and biochemically after purification by size-exclusion (SEC) and ion-exchange (IEC) chromatography. The enzyme from B. subtilis SMDFS 2B was characterized biochemically after partial purification by ii dialysis. Furthermore, the aspartic protease gene from A. oryzae DRDFS13 was characterized by cloning into Pichia pastoris using pGAPZαA as a vector and E. coli K12 for gene amplification. Finally a partially purified enzyme from A. oryzae DRDFS13 and B. subtilis SMDFS 2B used for Danbo cheese production using commercial rennet as a control. The Danbo cheeses produced using fungal enzyme (E1), bacterial enzyme (E2) and commercial rennet (C) were analyzed for body property, organoleptic characteristics, proximate and mineral composition when fresh and after 2 months of ripening. Seventeen fungi isolates were identified into different strains under the genera Aspergillus, Fusarium, and Pleurotus, whereas all the 14 bacterial isolates were identified to different strains under genus Bacillus. Moreover, A. oryzae DRDFS13 and B. subtilis SMDFS2B that showed enhanced MCA were selected for further study. The result from optimization and culture profile determination for A. oryzae DRDFS13 and B. subtilis SMDFS2B increased the MCA by 2.7 and 5.3 fold, respectively. The purified enzyme from A. oryzae DRDFS 13, IEC fraction A8 was exhibited a purification fold, specific activity, and yield of 6.20, 183.50 U/mg and 9.2%, respectively. The molecular weight of IEC A8 was 40 kDa, however, its MW was decreased to 30 KDa upon deglycosylation assay which infers that the protein is glycosylated. Inhibition study of IEC A8 with pepstatin A caused a 94 % inhibition on MCA. The dialyzed enzyme from A.oryzae DRDFS13 was shown maximum MCA at 60 oC and pH 5.0 with stability at pH 4.5-6.5 and temperature 35-45 0C. The partial purification of the crude enzyme from B. subtilis SMDFS 2B was increased its MCA by 2.0 fold. The dialyzed enzyme showed the highest MCA at 55 oC and pH 5.5 with stability at pH 4-6 and temperature 35 oC- 40 oC. The enzyme also showed the lowest residual MCA in the presence of EDTA (7.94%) and pepstatin-A (26.71%). The aspartic protease gene cloned into pGAPZαA (later pMKAP) was iii successfully expressed in P. pastoris and showed the highest MCA (190.47 U/mL) at pH 5 on the 6th day of incubation time. The recombinant protein has a MW between 32-46 kDa. Furthermore, the overall organoleptic characteristics, proximate composition, and mineral composition obtained from Danbo cheese made of A. oryzae DRDFS13 were closer to the control cheese produced using commercial rennet as compared to the bacterial enzyme. Therefore, the results from the present study confirmed that the enzyme from A. oryzae DRDFS 13 purified by an ion-exchange chromatography is an aspartic protease and could be used as a substitute for rennet enzyme in cheese production. This may open the way for applications of the enzymes in the food and dairy industries. Finally, the results from cheese production revealed that the fungal enzyme from A. oryzae DRDFS 13 is more appropriate for Danbo cheese production than the bacterial enzyme from Bacillus subtilis SMDFS 2B.
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    Characterization of Soil Fungi Capable of Striga Seed Bank Depletion Under in Vitro Conditions
    (Addis Ababa University, 2020-06-06) Bekele Mamo; Assefa Fassil (PhD)
    Striga hermonthica (Del.) Benth is an obligate hemi-parasitic plant which severely threatens cereal production. Therefore, the use of soil-borne antagonists for Striga seedbank depletion is one of the useful control methods suggested for integrated pest management (IPM). The objectives of this study were to preliminary screen and evaluate effective soil fungi that are capable of decaying Striga seed using seed trap method. From the soil samples showing seed decay, fungi were isolated and characterized using standard methods. The effect of fungal spores to inhibit Striga seeds germination was also tested using synthetic stimulant GR-24 and was further studied using sorghum variety Teshale. Besides, effects of fungal spore on Striga seeds viability were also studied. Soil samples collected from Tahtay Adiabo (E22) showed the highest Striga seed decay (19.8%) whereas soil samples collected from Raya-Kobo (E46) showed the lowest activity (3.6%). A total of 43 fungal isolates were collected from the soil of which 20 isolates decayed more than 50% of the Striga seeds. Genus Fusarium was the dominant and only ten further characterized. All isolates were showed maximum mycelium dry weight at 25oC and different mycelium dry weight at different hydrogen ion concentration (pH). Effects of fungal isolate on Striga seeds germination inhibition using sorghum variety Teshale as test crop revealed that there were significant (p<0.05) differences among fungal isolates. The results indicated that inoculation of the Striga seeds with isolate (F-254) significantly (p<0.05) have showed the highest percentage of Striga seed germination inhibition of 74.4%, 82.8% and 92.8% of all the fungal isolates upon 15, 21 and 30 days of incubation, respectively. In terms of Striga seed viability analysis, the highest number of Striga seed mortality (70%, 86% and 92%) were obtained when the Striga seeds treated with isolate (F-254) at 15, 21 and 30 days of incubation, respectively which were statistically significant (p<0.05) difference from all fungal isolates. However, the lowest results (16.4%) and (29.6%) were obtained from isolate (F-301) at 15 and 21 days of incubation while 39.6 ±8.98 was recorded at 30-DOI with isolate (F-040). This study therefore provides preliminary information on the existence of potential fungal isolates as candidates for biocontrol against Striga seeds in the soil that could be further tested in the management of Striga seedbanks.
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    Characterization of Striga Sp. Seed Bank Depleting Bacteria from Striga Infested Sorghum (Sorghum Bicolor (L.) Moench) Growing Areas of Northern and Eastern Ethiopia
    (Addis Ababa University, 2020-06-06) Yilma Getachew; Assefa Fassil (PhD)
    Striga hermonthica is a very devastative parasitic weed of (Sorghum bicolor (L.) Moench) which is the third important crop in Ethiopia. It is hemi-parasite living with the host plant by attaching small sucker root system to host plant. A study was undertaken to evaluate the effect of bacterial isolates obtained from soil samples collected from Striga infested sorghum growing fields in Amhara, Tigray and Oromia Regions to inhibit (deplete) the Striga seed bank. Surface sterilized and conditioned Striga seeds were buried in the soil by using teabag to determine germinated, viable and decayed seeds at different times after burial. A total of 44 isolates were isolated from germinated and decayed striga seeds and tested for their effect on germination and seed decay of Striga seeds. Six isolates (GS29, GS32, GS34, GS39, GS42 and GS45) were stimulated 10.33, 9.0, 9.67, 8.33, 5.33 and 8.33 Striga seeds germination from the total of 35 seeds respectively in the absence of host plant synthetic stimulant. On the other hand four isolates (SD3, SD9, SD36 and SD46) significantly decayed Striga seeds at P<0.05 (21, 20, 21.33 and 21 seeds respectively) in order to reduce Striga attack. Selected isolates were characterized by using biochemical tests, and three isolates were classified under the genus Pseudomonas while the other three isolates were grouped under the genus Klebsiella. The four isolates that showed seed decay were classified under the genus Bacillus.
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    Competitiveness and Symbiotic Effectiveness of Rhizobial Inoculants on Field Pea (Pisum Sativum) Under Greenhouse and Field Conditions
    (Addis Ababa Universty, 2017-06) Mekonnen Asrat; Assefa Fassil (PhD)
    Field pea (Pisum sativum) is widely cultivated in Ethiopia as a source of protein and integrated in crop rotation to improve soil fertility for it fixes nitrogen with rhizobia. However, effectiveness in nitrogen fixation depends upon the selection of symbiotically effective rhizobia to enhance production. Thus, a study was conducted to evaluate the performance of three inoculants; FBR 11, FBR 15, FBR 23 on growth, nitrogen fixation and yield under greenhouse and field conditions in relation to a commercial rhizobial strain 1018 at Kulumsa Agricultural Research Center during 2015/16 growing seasons. Standard physiological and biochemical tests were conducted to look into the nodule occupancy (competitiveness) of the three inoculants against the local rhizobia in the soil. The study showed that Isolate FBR 15 was the most effective inoculants with nodule occupancy of 75%, and were highly effective under greenhouse conditions, whereas the other inoculants were effective and occupied 50-60% of the nodules of the inoculated plants. Inoculation of field pea showed a highly significant (p≤0.001, p≤0.01 and p≤0.05) effect on all parameters compared to the uninoculated plants in the field trial. Accordingly, plants inoculated with isolate FBR15 and Strain 1018 showed a significant increase in nodule number (84-112NN/plant (10 times), NDW (77-94mg/plant) (12 times) against the un-inoculated control plants, and they also showed a 20-25% increase in both parameters in comparison to FBR11 and FBR23 inoculated plants. The treatments with FBR15 and the reference strain 1018 also showed significant difference in grain total nitrogen and N uptake and straw N uptake, and seed protein with 50-100% and 12-20% difference from the un-inoculated control plants and other Rhizobium treatments, respectively. Positive correlations were observed with respect to the number of nodule and shoot dry weight (r = 0.49, p<0.05), number of nodule and number of pod (r = 0.59, p<0.01), number of nodules and total grain yield (r = 0.56, p<0.05), and shoot dry weight and N content (r = 0.73, p<0.001). Although The MPN count of rhizobia in the soil at the experimental site was 1.5 x 104 and contained sufficient number of indigenous rhizobia, they were not effective that was indicated by the nodulation and yield parameters of the uninoculated treatments. The data in general, showed that the rhizobial inoculants, particularly FBR 15 was nutritionally versatile, ecologically competent, and symbiotically effective rhizobia compared to the commercial inoculant (strain 1018) that could be used as commercial inoculants for pea production after it is tested (validated) at different agro-ecological conditions. Key words: Biological yield, Grain yield, inoculation, nodule occupancy, N uptake.
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    The Effect of Storage Temperature and Time on Bacteriological Load and Physicochemical Quality of Nile Tilapia (Oreochromis niloticus) Fillet from Lake Tana, Ethiopia
    (Addis Ababa University, 2012-02) Yitayew Tizazu; Assefa Fassil (PhD)
    Fish and fish products are one of the food items that are of excellent nutritional source but it is highly perishable unless well preserved. Oreochromis niloticus (Nile Tilapia) is the most important fish species of Lake Tana fishery. Bacteriological load and physicochemical changes were evaluated during the storage of Nile Tilapia fillets at -18ºC and 5ºC for 30 days. The fish samples were collected from Lake Tana. Enumeration of Aerobic Colony Count, Enterobacteriaceae count and Psychrotrophic count; determination of protein, ash, and moisture contents, pH and TVB-N changes were undertaken. The analyses of all the parameters were carried out at regular 5 days interval on the fish fillets stored for up to 30 days. Data analysis were performed using SPSS version16 and Microsoft excel 2010. There was significant increase in Aerobic Colony Count, Enterobacteriaceae count and Psychrotrophic count on the fillets stored at 5ºC. The frozen condition showed significant effect on inhibiting all of the three groups of microbial counts. The moisture, protein, fat, and ash contents of fresh Nile tilapia fish fillets were 77.98%, 20.26%, 0.523% and 1.322%, respectively. The fillets stored at 5ºC showed significant decreases in protein and ash contents during 30 days of storage. On the other hand, there were no significant changes in moisture and ash contents of fillets kept under frozen condition for about 30 days. However, there was a significant decrease in crude protein content on the later days of storage under frozen condition. Moreover, TVB-N content of the fish fillets increased from 3.92 to 45.04 mgN/ 100g and 5.37 mgN/100g on samples kept at 5ºC and -18ºC, respectively. pH were also increased from 6.23 to 7.60 and 6.81 on the samples stored at 5ºC and -18ºC, respectively. The result shows that Nile Tilapia from Lake Tana had high protein content, low fat content, and high microbial load on fresh fillets, and freezing can keep the qualities of the fish relatively for longer period within safe levels and refrigeration could be able to keep the qualities briefly. Key words: Bacteriological load, Fresh, Oreochromis niloticus, Refrigeration, and TVB-N.
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    Effect of Two Azospirill Um Isolates on the Growth and Nitrogen Content of Tef (Eragrostis Tef (Zucc.) Trotter)
    (Addis Ababa University, 1998-06) Zewdie Solomon; Assefa Fassil (PhD); Fetene Masreha (PhD)
    Two diazotrophic bacteria, coded as A31 and A32, were isolated from roots of the lefvarieties DZ-01-354 and DZ-01-196, respectively grown in pots on loam soil from Debrezeit. These isolates were characterized to the generic level and further comparison with the description of the type cnltures Azospirillum lipoferum (ATCC 29707) and Azospirillum brasilense (ATCC 29145). These comparisons showed that the two isolates closely resemble A. lipofernm . However, on the basis of some differences in biochemical characteristics, it was suspected that these isolates may be different strains of A. lipoferum. In an attempt to investigate the effect of these isolates on the yield and nitrogen content of tef, inoculation studies on pot grown tef plants was conducted. Root inoculation of seedlings of the two tef varieties with Iml sterile water suspension (107-10' colony forming units (cfu) Iml ) of these isolates produced significant (p < 0.05) increases in height, grain yield, total shoot and root weight, root shoot ratio, total grain nitrogen and protein content of grains. Grain yield increases up to 11. 6 % and total nitrogen and protein content of grains up to 5.7 % over and above un inoculated controls were observed. The bacterial isolate A32 has performed better than A31 in promoting growth and yield of both varieties. Differential plant responses due to different bacterial treatments was found to be significant (p < 0.05) for parameters as height, root shoot ratio and total nitrogen and protein content of grains on both varieties. Of the two tef varieties Dz-01-196 responded better than DZ-O 1-354 to inoculation with either of the isolates as demonstrated in a higher percent increases over the respective controls for most growth parameters The existence of a possible specific interaction between host cultivar and bacterial isolate which governs plant yield responses was suspected. Finally, the potential role of Azospirillum inoculation of tef seedlings on reducing fertilizer requirements was discussed.
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    Effects of Land use Changes on Arbuscular Mycorrhizal Fungi Abundance and Diversity in Selected Agro-ecological Zones of Ethiopia: Implications for Sustainable Agro-ecosystems
    (Addis Ababa Universty, 2015-05) Belay Zerihun; Assefa Fassil (PhD)
    Arbuscular mycorrhizal (AM) filllgi association of six li'uit plant speeics [Mallgijera illdica L. (mango), l\1usa aculllinate Colla. (banana), Carica papaya L. (papaya), Citl'llS lilllOIl Risso. (lemon), Persea alllericana Mill. (avocado), and PsidiulII guajava L. (guava)] was investigated fi'om a low land area of Showa Robi!. Perecntage root colonization, spore abundance, species richness and diversity were examined. The resuit showed that ft'uit crops fell into higher spore density group of(7.2-8.8 spores g'l of soil) and low spore density group (3.7-5.3 spores g,t of soil). Accordingly, mango (1\1aJlgtfeJ'{[ il1dica), avocado (Persea americana), banana (J\1usa aCliminate), and Icmon (Citl'lIs lilllon) were fi'om thc high density spore group; whereas, papaya (Carica papaya), and guava (PsidiulII guqiava) fell into thc low spore density group at P <0.05. The AM colonization also showed that mango and lemon have high myeorrhization (71.7%), which guava has a low mycorrhization of27.3%. A total of 32 morpho species into 12 gencra were characterized fi'om all the fruit crops. The highest AMF species richness was in mango (18 species) followed by banana (16 species) and guava (14 spccies). The species Clal'OideoglolJlus c1aroideulli and Glolllus aggregatlIIn were the dominant specics ("generalists") among the fi'uit trees . . A total of 13 AMF species were detected in only one of the tested fruit trees, out of which foUl' species were recovered li'om mango indicating that the crops arc selective to specific mycorrhizal fill1gi. Key words: Arbuscular mycorrhizal fungi (AM F); GIOIIIIIS; Root colonization; Spore abundances
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    Ethanolic Extracts of Warburgia Ugandensis Against Some Test Microorganisms.
    (Addis Ababa University, 2010-04) Mekonnen Solomon; Assefa Fassil (PhD); Feleke Sisay (PhD)
    Warburgia ugandensis Sprague (Family: Canellaceae) is a tree that is highly utilized in traditional medicine in tropical and warm substropical countries of Africa. Crude ethanol extracts of leaves and heartwood of W. ugandensis were tested for in-vitro antimicrobial activity against six bacterial and a fungi test organisms using the disk diffusion method, agar well diffusion and broth dilution for minimum inhibitory concentration. E. coli was found to be the most susceptible bacterial isolate in the Agar well diffusion and Broth dilution. Meanwhile Shigella boydii was the most resistant bacterial isolate showing MIC value of 10mg/ml for the leaf extract. Bacillus subtilis was the second resistant bacterial isolate giving 0.0mm and 11.0mm inhibition diameter at disk diffusion assay and agar well diffusion, respectively. Streptococcus pneumoniae gave 2.5mg/ml and 5mg/ml MIC value for heartwood and leaf extracts, respectively. The same Minimum Inhibitory Concentration (MIC) value was recorded for B. subtilis. Pseudomonas aeruginosa showed the highest inhibition diameter (16.7mm) in the agar well diffusion assay for the heartwood extract. Staphylococcus aureus and Pseudomonas aeruginosa showed the same MIC value of 2.5mg/ml in leaf and heartwood extract. Candida albicans showed the highest inhibition diameter of 10.0mm and 30.7mm in disk diffusion and agar well diffusion, respectively at the highest test concentration (25mg/ml). In the broth dilution, a MIC value of 1mg/ml concentration of the leaf and heartwood extracts of W. ugandensis inhibited the growth of Candida albicans. It can be concluded that W. ugandensis has the potential as an antimicrobial agent in the future especially against C. albicans and E. coli. Key words: antimicrobial activity, Warburgia ugandensis, medicinal plants, leaf and heartwood extracts
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    Evaluation of Antagonstic Effect of Lactic Acid Bacteria Isolated From Ergo Against Selected Foodborne Pathogens Inoculated in to Ayib
    (Addis Ababa University, 2011-10) Mamo Jermen; Assefa Fassil (PhD); Tesfaye Anteneh (PhD)
    The antagonistic effects of mixed lactic acid bacteria cultures against foodborne pathogens (Staphylocuccus aureus ATCC 25923, Shigella boydii clinical isolate, Pseudomonas aeruginosa ATCC 25853) were evaluated on pasteurized ayib stored at room temperature. The lactic acid bacteria were tested for acid tolerance at pH 2, 2.5 and 3 for three and six hrs, bile tolerance for 24 and 48 hrs at 0.3% (W/V) bile salt concentration and antimicrobial effect on selected foodborne pathogens by co-culture assay in laboratory medium. Out of the 11 LAB isolates tested for acid tolerance 6 isolates showed survivals at pH 2.5 and pH 3 for 3 hrs and most isolates showed better tolerance to bile salt up on 24 and 48 hrs. Compared to the control (without any LAB bacteria), Ps. aeruginosa were inhibited by all six isolates to varying degree while, Sh. boyidii and S. aureus were inhibited by five of the isolates. Mixed LAB cultures of 106 cfu/g and test pathogens of 103 cfu/g were added together and separately in to ayib collected from Shola market and pasteurized. The effects of LAB against the foodborne pathogens were followed in ayib stored at ambient conditions for 9 days. The antagonistic effect of mixed LAB reduced the pathogens population by more than 2 log units on average on the 6 day. Complete elimination of the test organisms was achieved on day 5, 6, and 7 for Ps. aruginosa, S. aureus and Sh. boyidii respectively. The result indicated the mixed LAB cultures eliminate the test pathogen. Key words: Ayib, Lactic acid bacteria, foodborne pathogens, antimicrobial effect
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    Evaluation of Biological Control Agents Against Bacterial WiltPathogen (Xanthomonas campestris pv. musacearum) of Ensete(Ensete ventricosum)
    (Addis Ababa University, 2010-11) Tunasha Abayneh; Assefa Fassil (PhD); Tesfaye Alemu (PhD)
    The present study was designed with the objective of isolating, screening, evaluating and characterizing antagonistic isolates against bacterial wilt of ensete from rhizosphere and phyllosphere of the host. A total of 361 bacterial and 145 fungal colonies were isolated. The in vitro antagonistic test on the pathogen showed that 17 fungal isolates and 3 bacterial isolates were screened to be active against the pathogen on the appropriate media with inhibition diameters ranging from 5mm to 40 mm. This indicates that the bacterial antagonists were more effective than fungal antagonists to inhibit the test microorganism with inhibition diameters ranging from 32mm to 40mm whereas the fungal antagonists were more diverse in their effectiveness than bacterial antagonists with inhibition diameters from 5mm to 21mm. The most effective antagonistic isolates (AUFB1, AUFB2, AUFB2, AUFB11, AUFB17, AUFB15, AUbB, AUbB1 and AUbB2) were characterized and identified to their genus level. The isolates AUbB1, AUbB3 and AUbB3 (bacteria) were identified as Pseudomonas. The fungal isolates AUFB2 and AUFB11 were categorized into Trichoderma, isolates AUFB1, AUFB15 and AUFB19 were classified as Penicillium and the isolate AUFB3 was identified as Verticillium. These isolates were further tested for antagonistic and plant growth promoting properties. It has been found that two bacterial isolates AUFB1, AUFB2 produced indole acetic acid, protease and solubilize inorganic phosphate whereas the isolate AUbB3 (bacterium) produced hydrogen cyanide, indole acetic acid and solubilize inorganic phosphate. It was also recorded that two fungal isolates AUFB15 and AUFB11 produced HCN and protease but the isolate AUFB15 was also produced indole acetic acid and solublize inorganic phosphate. In vivo under green house condition four effective isolates AUbB3, AUbB1, AUbB2 (bacteria) and AUFB11 (fungus) were evaluated for their efficacy against the pathogen. The data showed that the isolates AUbB1, AUbB3, AUbB2 and AUbB11 reduced the disease severity of ensete wilt with DSR (disease severity reduction) 74.8, 62.4, 57.4, and 56.4%, respectively. The isolate AUbB1 (bacterium) showed highest DSR whereas the isolate AUbB11 (fungus) showed least DSR. The isolates which showed significance pathogen reduction in vitro test and under green house conditions should be checked under field trials to further confirm their efficacy and to use them as antagonists. The result will serve as base line data for future endeavor of utilizing biological control system of ensete to increase productivity into low-input agriculture of the regionand the country at large. Key words: Ensete, Xanthomonas campestris pv. musacearum, Fungal and bacterial antagonist
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    Evaluation of compost stability and maturity of floriculture solid waste in a Windrow System
    (Addis Ababa Universty, 2015-05) Sisay Abebe; Assefa Fassil (PhD)
    In Ethiopia, huge amount of flower residues are generated in each flower farm and damped into the environment leading to various problems. This initiated this work to utilize the wastes for soil amelioration and protection of the environment by composting via mixing the flower cuts with cow dungs (Pile1) and Effective Microorganisms (EM) plus molasses (Pile2) using Windrow method of compostingseparately in Ethio-highland and ZK farms. Samples were regularly taken from three locations of each pile for pyhsico-chemical and microbiological analysis over the 98 days of composting. The data showed three phases of temperature shifts, increase in macronutrients and TN as well as GI but reduction in C: N and NH4-N: NO3-N ratios and elimination of Agrobacterium spp. in both farms, in pile 1 and pile 2. In composting better in cow dung amended than EM plusMolasses added. The final compost products were found to be good quality in terms of plant nutrient, heavy metal and microbial composition. The composting activity of the flower cut should be encouraged and continued using cow dung in different flower farms to overcome environmental problems and use as fertilizer to improve agricultural productivity. Key words/phrases: Cow dung, Effective Microorganisms, ETH Flower, Frequent Turning, ZK flowers
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    Evaluation of Compost Stability and Maturity of Floriculture Solid Waste in a Windrow System
    (Addis Ababa Universty, 2015-05) Sisay Abebe; Assefa Fassil (PhD)
    In Ethiopia, huge amount of flower residues are generated in each flower farm and damped into the environment leading to various problems. This initiated this work to utilize the wastes for soil amelioration and protection of the environment by composting via mixing the flower cuts with cow dungs (Pile1) and Effective Microorganisms (EM) plus molasses (Pile2) using Windrow method of compostingseparately in Ethio-highland and ZK farms. Samples were regularly taken from three locations of each pile for pyhsico-chemical and microbiological analysis over the 98 days of composting. The data showed three phases of temperature shifts, increase in macronutrients and TN as well as GI but reduction in C: N and NH4-N: NO3-N ratios and elimination of Agrobacterium spp. in both farms, in pile 1 and pile 2. In composting better in cow dung amended than EM plusMolasses added. The final compost products were found to be good quality in terms of plant nutrient, heavy metal and microbial composition. The composting activity of the flower cut should be encouraged and continued using cow dung in different flower farms to overcome environmental problems and use as fertilizer to improve agricultural productivity. Key words/phrases: Cow dung, Effective Microorganisms, ETH Flower, Frequent Turning, ZK flowers
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    Evaluation of Millenium Development Goal for Control of Tuberculosis (Tb) in Nekemte Town (2010/11– 2014/15)
    (Addis Ababa University, 2016-08) Lechissa Ajema; Assefa Fassil (PhD)
    Tuberculosis (TB)is one of the major public health problem wide spread world wide.AS Global TB report of 2014 showed, in 2013 alone there were about 9.0million newly infected and 1.5 million deaths. The problem was worse in Africa where our country Ethiopia is found. The present study was carried out in Nekemte town, one of the areas highly affected by the disease. The aim of the study was to examine the prevalence of ‘all TB cases’ in the study area in sex and age category, case detection rate(CDR), those co-infected with HIV and the treatment outcome of those attended DOTS(Directly Observed Therapy - Short course) service in the three government health care facilities found in Nekemte town in relation to MDG. A retrospective cross-sectional study design based on document analysis of TB Registry Unit of the patients found in the TB Center was used. The study results revealed that there were1246TB cases registered on the TB Registry Units in the five years (2010/11-2014/15) period of the study. Out of these cases644(51.7%) were males and 602(48.3%) females. Ninety eight point one percent(98.1%) of the cases were new TB cases. Results of age specific prevalence of TB cases revealed that the majority 1124(90.2%)patients were within the active productive age group(15 -64 years)that made TB a dangerous disease that affects the economy of the individual, family and the country as a whole. The case detection rate (CDR) in the study area was 38.9% which was lower than the national (62%),Regional(Africa)52% and global 64%. The area is not on track to meet the global target of 70% CDR by2015. In this study area, all TB patients were tested for HIV, indicating it has met the global target(100%) by 2015.The prevalence of TB/HIV co-infection in the study area was higher(18.7%) compared to the national prevalence (11%), that requires a collaborative activity of TB and HIV control program. Results for treatment outcome showed an overall treatment success rate of 85.5% .The treatment success rate of this study area has met the global target of 85%by 2015,but is lower to the national achievement of 91%, suggesting an improvement . Keywords: Tuberculosis, TB/HIV co-infection, Prevalence, case detection rate, Treatment outcome, treatment success rate
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    Evaluation of Nitrogen Removal Rates from Abattoir Wastewater in a Pilot Predenitrification-Nitrification Activated Sludge Wastewater Treatment Plant
    (Addis Ababa Universty, 2005-07) Woldesenbet Fantahun; Assefa Fassil (PhD)
    Abattoir wastewater has a complex.composition and is very harmful to the environment. It causes eutrophication, suffocation of aquatic life and contamination of ground water. Nitrogen is the main component of the abattoir wastewater. Because of environmental and health problems they cause, nitrogen compounds should be reduced to the acceptable discharge limit level before the wastewater is released to water bodies and the environment. Biological methods of nitrogen removal are considered to be cost effective and environmentally friendly alternatives than chemical treatment. The objectives of this study were therefore: to evaluate the treatment processes of a predenitrification-nitrification activated sludge system for abattoir wastewater treatment; Characterize the activated sludge involved in the treatment process through Ammonium uptake rate and Nitrate uptake rate, and its seUlability by sludge volume index. Abattoir wastewater was sampled from Addis Ababa Abattoirs Enterprise, analyzed for selected parameters to check its biodegradability and fed into a predenitrification nitrification activated sludge wastewater treatment system at varying operational parameters. The removal efficiency for the selected parameters and the characteristics of the sludge at each operational condition was evaluated. A removal efficiency of 94- 98% for COD, 95-99% for BOD5, 85-97% for total nitrogen, 58-95% for AmmoniumNitrogen and 46-53% reduction in phosphate was obtained in the treatment processes. The predenitrification-nitrification rates measured as Ammonium Uptake Rate and Nitrate Uptake Rate ranged from 5.9-9.8 mg NH4-N/gVSSh and 8.2-12.1 mg N03- N/gVSSh respectively. The sludge volume index (SVI) ranged from 51.5 mUg to 87.6 mUg. The abattoir wastewater was found to be suitable for biological wastewater treatment. It is also showed that the predenitrification-nitrification system was efficient in organic matter and nitrogen removal from abattoir wastewater.