- Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University. PoB 2713 Doha, Qatar
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- Dr. Nabil Zouari is Full-Professor of Biology and Environmental Microbiology at Qatar University, College of Arts and... moreDr. Nabil Zouari is Full-Professor of Biology and Environmental Microbiology at Qatar University, College of Arts and Sciences, Department of Biological and Environmental Sciences. He obtained his PhD degree in Microbiology, Enzyme Engineering & Bioconversion from the University of Technology of Compiègne (UTC, France). Dr Nabil is also engineer in biological engineering. He has 33 years of experience in Teaching and Research & Development in the fields of Environmental Technology, Enzyme Engineering, Industrial Microbiology and transfer of technology in France, Tunisia and Qatar. Dr. Nabil published more than 60 papers in international indexed journals, covering all his fields of specialization. He developed 6 industrial applications in the field of agro-industry. He has an experience of ten years in the field of results development and valorization and incubation of innovations ( in France and Tunisia) and created one start-up in the field of biotechnology. He has experience in leading and directing research projects, UG and graduate research supervision (dozens of theses) and graduate studies coordination as well.edit
Sludge generation as an organic by-product of wastewater treatment has seen a consistent increase worldwide due to population growth and industrial activities. This poses a chronic challenge regarding management options and environmental... more
Sludge generation as an organic by-product of wastewater treatment has seen a consistent increase worldwide due to population growth and industrial activities. This poses a chronic challenge regarding management options and environmental concerns. The agricultural valorization of unconventional organic materials has become inevitable, especially in semi-arid and arid countries that suffer from depleted soils and shortages in farm manure supply. High-income countries have also been interested in this recycling practice to mitigate landfilling or incineration issues. Sewage and some industrial sludges contain a complex mixture of beneficial and harmful substances, which varies with the origin of effluents. Therefore, sludge land application should be well managed in order to achieve sustainable agro-environmental goals. This review paper focuses on different aspects related to sludge reuse in agriculture, starting by investigating the diversity of sludge types and composition. In addi...
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Air-conditioning systems make the most significant part of energy consumption in the residential sector. There is no denying that it is essential to produce a comfortable indoor thermal environment for residents in a building. The actual... more
Air-conditioning systems make the most significant part of energy consumption in the residential sector. There is no denying that it is essential to produce a comfortable indoor thermal environment for residents in a building. The actual goal is to achieve thermal comfort level without putting too much cost on the ecological system by trying to conserve the amount of energy consumed. An effective way to help achieve such a goal is by incorporating thermal insulation in buildings. Thermal insulations help reduce thermal energy gained during the implementation of a desired thermal comfort level. This study aims to use an environmentally friendly nanoparticle of date pits to create thermal insulations that can be used in buildings. Different ratios of the nanoparticle of the date pits and sand composite were investigated. Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize the new materials. The material with nanoparticles of date pits and...
Research Interests: Environmental Science, Materials Science, Architecture, Biomaterials, Sustainable Building Design, and 14 moreEnergy Consumption, Nanomaterials, Nanotechnology, Environmental Sustainability, Medicine, Multidisciplinary, Thermal comfort, Thermal, PLoS one, Thermal Conductivity, Thermal Insulation, Thermal Insulation Coating, Sustainability, and environmentally friendly
Carbonates with a mol% of Mg above 40 were obtained exclusively in the presence of organic molecules. The mode used to add carbonate to the solution obtaining supersaturation has a significant impact on the forming mineral phase.
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Aeolian processes produce vast areas of sand and dunes in the arid region and need monitoring since they are encroaching land and degrading infrastructures. In this study, we used the satellite data of ASTER and mineral indices namely... more
Aeolian processes produce vast areas of sand and dunes in the arid region and need monitoring since they are encroaching land and degrading infrastructures. In this study, we used the satellite data of ASTER and mineral indices namely quartz index (QI) and carbonate index (CI), and identified and discriminated the sand deposits, dunes, and associated rock formations that occurred in and around the QAFCO site 5/6, Qatar. The mapping of the area using high spatial resolution WorldView-2 satellite data confirmed the presence of sand deposits, dunes, and sand encroachments in the site. Our field studies validated the satellite data results. The grain size analyses of samples showed that the deposits have predominantly sand grains (81.3 to 99.81 %). The XRD analyses of samples identified the presence of quartz, calcite, dolomite, albite, and halite minerals. These are confirmed by geochemical analyses, which showed the high concentration of SiO2, Al2O3, CaO, MgO, Na2O, CO3, SO4, Cl, and ...
Research Interests: Geology, Qatar, Quartz, Stabilization, Carbonate, and 4 moreDolomite, Calcite, Aeolian Deposits, and Arid
Purpose of Review This paper reviews various low-cost treatment techniques such as adsorption, permeable reactive barrier, and biological techniques for the simultaneous removal of chemical and microbial contaminants from groundwater and... more
Purpose of Review This paper reviews various low-cost treatment techniques such as adsorption, permeable reactive barrier, and biological techniques for the simultaneous removal of chemical and microbial contaminants from groundwater and discusses treatment mechanisms of different treatment techniques. This paper also discusses the challenges of groundwater treatment, how to choose the appropriate treatment technique, and cost analysis of groundwater treatment. Recent Findings Various treatment technologies have been used for the treatment of groundwater: physical, chemical, and biological technologies with different success rates. In the literature, various adsorbents have been successfully synthesized from low-cost and environmentally friendly materials. Adsorption is considered an efficient treatment technique for the removal of both toxic elements and pathogens by utilizing different adsorbents. For example, the nanostructures of MgO with a BET surface area of up to 171 m2/g obt...
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Pseudomonas fluorescens Pf1TZ was inhibitory in vitro to a number of phytopathogenic fungi and could protect vine plantlets against Botrytis cinerea. Total protection was reached after 3 weeks of bacterial inoculation. The endophytism of... more
Pseudomonas fluorescens Pf1TZ was inhibitory in vitro to a number of phytopathogenic fungi and could protect vine plantlets against Botrytis cinerea. Total protection was reached after 3 weeks of bacterial inoculation. The endophytism of Pf1TZ was confirmed by confocal microscopy using its inherent fluorescence. The molecular characterization of Pf1TZ indicated the presence of genes from clusters encoding pyoluteorin and phenazine. The chromatographic purification and LC-MS(n) analysis revealed that the most active one has a molecular mass of 504 Da.
Research Interests: Engineering, Microbiology, Mass Spectrometry, Biology, Confocal Microscopy, and 15 moreMedicine, Biological Sciences, Botrytis, Bacteria, Phenazines, Gene, Antifungal Activity, High Performance Liquid Chromatography, Gen, Molecular Characterization, Botrytis cinerea, Molecular Mass, Molecular weight, Biosynthetic Pathways, and Antibiosis
Research Interests: Chemistry, Food Science, Computational Biology, Experimental Design, Biological Sciences, and 15 moreBacillus, Antifungal, Antifungal Activity, Aspergillus niger, CHEMICAL SCIENCES, Fermentation, Bacterial Load, Antifungal Agents, Bacillus Amyloliquefaciens, Central Composite Design, Culture Media, Ferric Compounds, Copper sulfate, Chlorides, and culture medium
Chitinases have been successfully used in combination with Bacillus thuringiensis delta-endotoxins forming crystals in order to enhance their insecticidal activities. In this context, we opted for promoting the chitinase integration into... more
Chitinases have been successfully used in combination with Bacillus thuringiensis delta-endotoxins forming crystals in order to enhance their insecticidal activities. In this context, we opted for promoting the chitinase integration into these crystals. Thus, we engineered, for the first time, a fusion protein (CDF) consisting of the chitinase Chi255 and the carboxy-terminal half of Cry1Ac, both from B. thuringiensis subsp. kurstaki. The constructed transcriptional fusion (chi255Δsp-CTcry1Ac) was cloned into a shuttle vector (Escherichia coli/B. thuringiensis) downstream the sporulation-dependent promoters BtI-BtII and upstream the cry1Ac transcription terminator. The resulting plasmid, named pF, was transferred by electroporation to crystalliferous B. thuringiensis strain BNS3 and acrystalliferous strain BNS3Cry-. The functionality of the chimerical chitinase was demonstrated by an improvement of the relative chitinolytic activity of the recombinant strain BNS3/pF by 2.5 folds. Western blot analyses showed that, despite of the instability of CDF when expressed in the acrystalliferous strain, the C-terminal half of Cry1Ac succeeded to allow the integration of the chimerical chitinase into the crystal of BNS3. The recombinant strain BNS3/pF (LC(50) = 144.06 μg g(-1)) was 1.5 times more active against Ephestia kuehniella larvae than the wild strain (LC(50) = 212.10 μg g(-1)).
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Research Interests: Engineering, Chemistry, Environmental Biotechnology, Optimization, Biological Sciences, and 15 moreBacillus thuringiensis, Bacteria, Fermentation, Oxygen, Biopesticide, Dissolved Oxygen, Large Scale, Microbial enzyme Technology, Aeration, Industrial Fermentation, Point of View, Culture Media, Carbon Source, Catabolite Repression, and Oxygen saturation
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Research Interests: Environmental Science, Soil, Adaptation, Bioremediation, Biology, and 15 moreEnvironmental Chemistry, Biodiversity, Medicine, Hydrocarbon, Bacteria, Nitrogen, Bioaugmentation, Biomed, Soil Microbiology, HYDROCARBONS, Diesel Fuel, GAS LIQUID CHROMATOGRAPHY, Biostimulation, Gasoline, and Petroleum Pollution
... The following minerals were used (g dm −3 ): KH 2 PO 4 , 1; K 2 HPO 4 , 1; MgSO 4 , 0.3; MnSO 4 , 0.01 and FeSO 4 ... high purity of the crude solubilized crystal proteins from gruel-and fish meal-based media was proven by SDSPAGE... more
... The following minerals were used (g dm −3 ): KH 2 PO 4 , 1; K 2 HPO 4 , 1; MgSO 4 , 0.3; MnSO 4 , 0.01 and FeSO 4 ... high purity of the crude solubilized crystal proteins from gruel-and fish meal-based media was proven by SDSPAGE analysis as described by Zouari and Jaoua ...
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Nutritional requirements of a strain ofBacillus thuringiensis (Bt) subsp.kurstaki were elucidated for δ-endotoxin production. The effect of some principal nutrients was deeply investigated, showing several nutritional and metabolite... more
Nutritional requirements of a strain ofBacillus thuringiensis (Bt) subsp.kurstaki were elucidated for δ-endotoxin production. The effect of some principal nutrients was deeply investigated, showing several nutritional and metabolite limitations in Bt growth and δ-endotoxin synthesis. This led us to formulate a new medium based on the hydrolysate of gruel, a cheap and abundant byproduct of semolina factories, supporting growth and
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BUPM4 is a Bacillus thuringiensis subsp. kurstaki strain, isolated from Tunisian soil, producing an original bacteriocin named Bacthuricin F4. The optimization of the latter production conditions was carried out under several... more
BUPM4 is a Bacillus thuringiensis subsp. kurstaki strain, isolated from Tunisian soil, producing an original bacteriocin named Bacthuricin F4. The optimization of the latter production conditions was carried out under several physicochemical conditions. It was found that the highest bacteriocin activity was reached at low aeration while bacteriocin synthesis yields were strongly reduced at higher ones. A balance between growth and bacteriocin synthesis, both highly dependent on aeration, was taken into account for the overproduction of bacteriocin. Both glucose and glycerol were shown to be necessary for Bacthuricin F4 maximal synthesis. In addition, the optimal carbon/nitrogen ratio for bacteriocin production is 9. In such optimal conditions, more than 4-fold greater bacteriocin production was obtained than when using TSB medium.
Research Interests: Chemistry, Technology, Food Science, Carbon, Medicine, and 14 moreQuality Control, Biological Sciences, Bacillus thuringiensis, Bacteriocins, Nitrogen, Bacteriocin, CHEMICAL SCIENCES, Glycerol, Bioreactors, Cell Proliferation, Aeration, Optimality Condition, Overproduction, and Cell culture techniques
Research Interests: Microbiology, Mass Spectrometry, Biology, Fungi, Medicine, and 15 moreBiological Sciences, Plant diseases, Bacteria, Antifungal Activity, Aspergillus niger, High Pressure Liquid Chromatography, Burkholderia, Antifungal Agents, Base Sequence, Burkholderia Cepacia, Burkholderia Cepacia Complex, Phytopathogenic Fungi, Molecular Structure, Nuclear Magnetic Resonance Spectroscopy, and biological control agents
The effect of Bacillus thuringiensis cry gene copy-number on δ-endotoxin production and on toxicity has been investigated. When a wild-type strain of B. thuringiensis kurstaki, BNS3, was transformed with the recombinant plasmids... more
The effect of Bacillus thuringiensis cry gene copy-number on δ-endotoxin production and on toxicity has been investigated. When a wild-type strain of B. thuringiensis kurstaki, BNS3, was transformed with the recombinant plasmids pHTcry1Aa, pHTcry1Ac, and pHTcry2Aa, δ-endotoxin synthesis was enhanced by 269, 267, and 243%, respectively. In contrast, spore counts were decreased by at least 50% which was attributed to
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The optimization of antifungal activity production by Bacillus amyloliquefaciens was carried out using Response Surface Methodology (RSM) in two steps. The first step involved the screening of cultural parameters affecting the production.... more
The optimization of antifungal activity production by Bacillus amyloliquefaciens was carried out using Response Surface Methodology (RSM) in two steps. The first step involved the screening of cultural parameters affecting the production. The second step involved the optimization of significant ones. In this study, we used Bayesian network to predict the results of the experiments required for the second step. Then, by RSM, using the predicted values by BN, we defined the composition of a culture medium allowing 56% improvement in antifungal activity production over the basal medium. Such medium composition and improvement were shown to be similar to that obtained in the previous study demonstrating that, when coupled with RSM, BN permitted improvement of antifungal activity production with a much reduced number of experiments.
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Bacillus thuringiensiskurstaki is a soil bacterium that produces insecticidal toxins called delta-endotoxins. In order to increase the toxic crystal concentrations in a low-cost culture medium and thus improve the biopesticide quality to... more
Bacillus thuringiensiskurstaki is a soil bacterium that produces insecticidal toxins called delta-endotoxins. In order to increase the toxic crystal concentrations in a low-cost culture medium and thus improve the biopesticide quality to control insect pests, the Plackett–Burman screening method was applied. It was shown a tool to evaluate the significance of the selected seven factors (KH2PO4, K2HPO4, MgSO4, MnSO4, FeSO4, soybean meal, starch) which are necessary to the production of the delta-endotoxins. This was performed into two different shake flasks (250 and 500 ml). The main factors that affected the production of delta-endotoxins are shown to be soybean meal, starch, and FeSO4 in 250 ml culture flasks. In 500 ml culture flasks, soybean meal and FeSO4 are the principal factors influencing the delta-endotoxin production. The multiple linear regression, a method applied as the merging dataset of the two Plackett–Burman designs, established that soybean meal and starch are the factors positively affecting the production of delta-endotoxins, in contrast to FeSO4. Furthermore, the available oxygen in culture flasks showed no significant negative effect on delta-endotoxin production. This study revealed that mixed method designs were useful to identify the significance and the effect of hidden culture parameters.
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The acquisition of the erythromycin resistance by Bacillus thuringiensis kurstaki improved yields of delta-endotoxins in sporulating cells ranging from 134 to 215%. Resistance to erythromycin decreased the final spore count by at least... more
The acquisition of the erythromycin resistance by Bacillus thuringiensis kurstaki improved yields of delta-endotoxins in sporulating cells ranging from 134 to 215%. Resistance to erythromycin decreased the final spore count by at least 50%. Consequently, erythromycin resistance is an efficient tool for the improvement of bioinsecticides yields with a high ratio of delta-endotoxins to spores.
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Research Interests: Chemical Engineering, Food Science, Biomedical Engineering, Polymorphism, Biology, and 15 moreAgricultural Biotechnology, Medicine, Lepidoptera, Insecticides, Incubation, Animals, Nitrogen, Bioinsecticide, Larva, Biological Pest Control, Large Scale, Culture Media, Production Cost, Photorhabdus, and biological control agents
The use of bioinsecticides, particularly those produced by sporeless Bacillus thuringiensis strains, has been shown to be a good alternative in pest management. Two types of sporeless mutants were distinguished. The asporogenic mutants... more
The use of bioinsecticides, particularly those produced by sporeless Bacillus thuringiensis strains, has been shown to be a good alternative in pest management. Two types of sporeless mutants were distinguished. The asporogenic mutants which completely lack spores produce a regular bipyramidal crystal inclusion. The oligosporogenic mutants kept the ability to produce insecticidal crystal proteins. However, sporulation in such mutants was not totally blocked and very few of them could still produce spores. In order to improve bioinsecticides production, adaptation of sporeless strains to heat shock and osmotic stress was investigated. Delta-endotoxin production by 78% of sporeless mutants was significantly improved by osmotic stress with an overproduction of about 17%, compared to the wild strain BNS3. However, toxin production was improved by only 21% of mutants after heat shock, in low cost medium. The statistical analysis proved that delta-endotoxin production, cell growth, and spore formation of asporogenic and oligosporogenic mutants depended on the type of applied stress. Each strain has an important potential when applying the adequate stress. Moreover, adaptation of sporeless mutants to NaCl may allow the substitution of all minerals of the medium by diluted sea water which appeared to be a good alternative for the economic production of bioinsecticides at industrial scale which is of great importance from the practical point of view.
Research Interests: Microbiology, Pest Management, Medical Microbiology, Biology, Medicine, and 15 moreInsecticides, Bacillus thuringiensis, Osmotic pressure, Sea Water, Heat Shock, Physiological Stress Markers, Osmotic Stress, Point of View, Culture Media, Spore, Endotoxins, Cell Growth, Nitrous acid, Osmotic Shock, and insecticidal crystal protein
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ABSTRACT Bacillus thuringiensis is a Gram positive bacterium that produces an insecticidal crystalline protein making it one of the most important biocontrol agents for pest management. Bioinsecticides based on B. thuringiensis were... more
ABSTRACT Bacillus thuringiensis is a Gram positive bacterium that produces an insecticidal crystalline protein making it one of the most important biocontrol agents for pest management. Bioinsecticides based on B. thuringiensis were produced by fermentation processes in liquid media. Cultural conditions controlling proteolytic activities in different culture media were investigated to study the possible correlations between B. thuringiensis production of proteases and delta-endotoxins in a low-cost complex medium. Aeration appeared to play an important role in delta-endotoxin production. The correlation between proteolytic activity and aeration does not seem to be reliable. A negative correlation (correlation coefficient =− 0.774) was established between protease activity and delta-endotoxin production. In order to prove this correlation, protease hypo-producing and overproducing mutants were isolated through random mutagenesis of two wild strains, BUPM13 and BUPM5, by using nitrous acid. Interestingly, delta-endotoxin production of BUPM13-1, BUPM13-2 and BUPM13-3 was markedly improved when compared to the wild strain BUPM 13, reaching 2.1-fold, 3.69-fold and 8.13-fold, respectively. Maximal protease activity (540-2468 UI) obtained by BUPM5-1 and BUPM5-2 was 2.34-fold and 10.7-fold, respectively, more than that obtained by the wild strain BUPM5 with a drastic decrease of their delta-endotoxin production. Study of delta-endotoxin production by the selected mutants confirmed that insecticidal crystal protein stability in the culture strongly depends on the level of endogenous protease activity. This was also confirmed by bioassays measuring the LC50 using larvae of Ephestia kuehniella. Determining protease activity in fermentation culture could be useful in indirectly predicting the potency of B. thuringiensis strains with high insecticidal activities. This would allow low-cost selection of overproducing wild isolates or mutants in the screening programmes for the reduction of production cost, which is important from a practical point of view.
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The present work aimed to obtain bioinsecticide over-producing mutants through classical mutagenesis of vegetative cells of Bacillus thuringiensis (Bt) by using u.v. and nitrous acid, and to evidence the involvement of cell metabolism in... more
The present work aimed to obtain bioinsecticide over-producing mutants through classical mutagenesis of vegetative cells of Bacillus thuringiensis (Bt) by using u.v. and nitrous acid, and to evidence the involvement of cell metabolism in delta-endotoxin synthesis. Vegetative cells of Bt were treated by nitrous acid (0.17 mg ml(-1)) or exposed to u.v. rays (emitted at a wave length of 240 nm). The isolated survivors were screened on the basis of the production of delta-endotoxins and biomass in glucose and/or in gruel-based media at two aeration conditions. Bioinsecticide over-producing mutants were obtained with high frequencies because random mutations were shown to affect cell metabolism at different pathways related to the regulation of delta-endotoxin synthesis. Classical mutagenesis of Bt cells lead to the isolation of a large variety of delta-endotoxin over-producing mutants that could be classified into six groups based on the location of the mutations, particularly in metabolism pathways and delta-endotoxin synthesis. High frequencies of delta-endotoxin over-producing mutants of Bt could be obtained through classical mutagenesis of vegetative cells. This should contribute to a significant reduction of production and utilization costs of Bt bioinsecticides.
Research Interests: Metabolism, Biomass, Adaptation, Biology, Heat Treatment, and 15 moreApplied microbiology, Medicine, Insecticides, Bacillus thuringiensis, Glucose, Bacterial Toxins, Bacteria, Fish Products, Biopesticide, Heat Shock, Biological Pest Control, Metabolic pathway, Culture Media, Cell Survival, and Endotoxins
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An environmental Burkholderia cepacia strain named Cs5 was isolated and identified first using API biochemical identification system and then with 16S rDNA and recA sequence homology search. This bacterium exhibited a broad spectrum of... more
An environmental Burkholderia cepacia strain named Cs5 was isolated and identified first using API biochemical identification system and then with 16S rDNA and recA sequence homology search. This bacterium exhibited a broad spectrum of fungicidal activities against Alternaria alternata, Aspergillus niger, Fusarium culmorum, F. graminearum, F. oxysporum and Rhizoctonia solani. In the liquid conditions, the MIC of A. niger and R. solani were reached with, respectively, 1.25-2% of the Cs5 liquid culture supernatant. However, in the solid conditions, the same inhibition was caused in the presence of 3% of the Cs5 supernatant. The exhibition of these two fungi at low concentrations of supernatant Cs5 caused various morphological changes of their mycelia which were observed by confocal microscopy. Three antifungal compounds, named Cs5-255, Cs5-257 and Cs5-446, were purified from the Cs5 culture. The structural analysis of these molecules showed that Cs5-255 and Cs5-257 are analogous and belonged to the alkyl-quinolone family, while Cs5-446 was a didecyl-phthalate, isolated for the first time from a bacterium.
Research Interests: Microbiology, Medical Microbiology, Biology, Fungi, Confocal Microscopy, and 15 moreMedicine, Plant diseases, Antimicrobial activity, Quinolones, Aspergillus niger, Aspergillus flavus, Alternaria alternata, Fusarium oxysporum, Current, Burkholderia, Prunus, Antifungal Agents, Burkholderia Cepacia, Molecular Structure, and Mycelium
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This research focuses on investigating the effectiveness of microbial-induced carbonate precipitation (MICP) to reduce the potential for wind erosion. This paper summarizes the results of preliminary wind tunnel experiments. Wind tunnel... more
This research focuses on investigating the effectiveness of microbial-induced carbonate precipitation (MICP) to reduce the potential for wind erosion. This paper summarizes the results of preliminary wind tunnel experiments. Wind tunnel experiments were performed on untreated and MICP-treated samples. Soil samples prepared at the same relative density were treated using different treatment procedures. Soil samples were sprayed with bacteria (Sporosarcina pasteurii) suspended in a urea solution followed by the application of a calcium chloride cementation solution. The solutions were applied on the soil surface and allowed to percolate through the sample. To determine the wind velocity profile in the wind tunnel, pitot tubes were used to measure the differential pressure at various heights and verified analytically using the law of the wall. Digital image correlation (DIC) combined with wind velocity measurements were utilized to identify the conditions at which the surface fails (i.e., erosion initiation and sustained erosion). The wind velocity was gradually increased until particle movement was initiated. This paper summarizes the experimental setup and results of preliminary experiments. - 2019 American Society of Civil Engineers.This work was made possible by an NPRP8-1929-2-766 a grant from the Qatar NationalScopu
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Weathering processes change properties and composition of spilled oil, representing the main reason of failure of bioaugmentation strategies. Our purpose was to investigate the metabolic adaptation of hydrocarbon-degrading bacteria at... more
Weathering processes change properties and composition of spilled oil, representing the main reason of failure of bioaugmentation strategies. Our purpose was to investigate the metabolic adaptation of hydrocarbon-degrading bacteria at harsh conditions to be considered to overcome the limitations of bioaugmentation strategies at harsh conditions. Polluted soils, exposed for prolonged periods to weathered oil in harsh soils and weather conditions, were used. Two types of enrichment cultures were employed using 5% and 10% oil or diesel as sole carbon sources with varying the mineral nitrogen sources and C/N ratios. The most effective isolates were obtained based on growth, tolerance to toxicity, and removal efficiency of diesel hydrocarbons. Activities of the newly isolated bacteria, in relation to the microenvironment from where they were isoalted and their interaction with the weathered oil, showed individual specific ability to adapt when exposed to such factors, to acquire metaboli...
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This study investigates the concomitant removal of hydrocarbons and heavy metals by highly adapted Bacillus and Pseudomonas strains. In regions characterized by harsh conditions such as Qatar, the weathering processes would affect the... more
This study investigates the concomitant removal of hydrocarbons and heavy metals by highly adapted Bacillus and Pseudomonas strains. In regions characterized by harsh conditions such as Qatar, the weathering processes would affect the content, status, and distribution of these contaminants. It was shown in the weathered soil from Dukhan oil wastes dumpsite that 14 heavy metals exceeded the EPA limits. Moreover, it was demonstrated that soil organics did not affect the distribution of the metals in the soil. However, most of the heavy metals were strongly bonded to the residual and the iron-manganese oxide fractions. Eighteen bacterial strains isolated from highly weathered oily soils were able to grow with heavy metal concentrations up to 3 mM and above for some. Seven selected strains (4 Bacillus and 3 Pseudomonas) showed the ability to remove almost 60 to 70% of most of the heavy metals when used at 1 mM. Moreover, they removed up to 75% of the diesel range organics. These results...