Laila A. Farahat

Biodegradation of Baleym Mix Crude Oil in Soil Microcosm by Some Locally Isolated Egyptian Bacterial Strains

Petroleum refining, transportation and storage are sources of soil contamination. In Egypt, a large number of contaminated sites exist as a result of different crude oil activities. In this work, biodegradation experiments in artificially oil contaminated soil microcosms (30 cm × 26 cm × 8 cm) of shallow polypropylene plastic trays were carried out with special emphasis on biodegradation of polycyclic aromatic hydrocarbons (PAHs). Two promising isolates, Pseudomonas aeruginosa I.1.1.6 and Brevibacterium casei I.2.1.7, previously isolated from Egyptian hydrocarbon contaminated soil, were used. The microcosms were inoculated at 30°C for 60 days with a water content of 60%wt. TPH were quantitatively monitored, gas chromatographic (GC) and high performance liquid chromatographic (HPLC) analysis were preformed to follow up the biodegradation process. The results obtained indicate that after 60 days of incubation; Pseudomonas aeruginosa I.1.1.6 showed higher TPH biodegradation efficiency (64%) than that of Brevibacterium casei I.2.1.7 (58%). Bacterial isolates I.1.1.6 and I.2.1.7 showed total normal alkanes degradation of approximately 74% and 90%, respectively. Generally they are capable of degrading high molecular weight PAHs (five and six membered ring compounds, benzo[b]fluoranthene; BbF and indeno[1,2,3-cd]Pyrene, IP, and have broad versatility in their action on the16PAH compounds currently regulated by the US Environmental Protection Agency (EPA) as priority pollutants, and could be useful in bioremediation of soil contaminated with crude oil.

Non-Newtonian behaviour of yeast suspensions

SummaryThe rheological properties of yeast (Bakers yeast) suspensions in water and in water-methanol-electrolyte solutions have been investigated using a Fann V.G. concentric cylinder viscometer. The resulted rheograms could be described by the power law model for non-Newtonian fluids with the flow behaviour index “n”<1 indicating pseudo-plastic behaviour. This flow behaviour index was constant under all operating conditions while the consistancy index “k” increased exponentially with increasing wet yeast volume fraction. The addition of methanol and electrolytes had a negligible effect on the rheological properties. Changing the pH of the suspension acidic to lowered the apparent viscosities.

The Evaluation of Different Bioremediation Processes for Egyptian Oily Sludge Polluted Soil on a Microcosm Level

In this study, bioremediation of an Egyptian oily sludge polluted soil with total petroleum hydrocarbon content of 53,100 mg kg−1 was achieved on a microcosm level at 30°C over a 180-day period. The analysis of variance revealed that soil microcosms biostimulated with corn steep liquor and bioaugmented with Micrococcus lutes RM showed significant removal of total petroleum hydrocarbon relative to natural attenuation microcosms; recording total petroleum hydrocarbon removal of 44 and 54% with p = 0.004 and p = 7.69e-5, respectively. Kinetic study revealed that the degradation processes followed the first-order model. Bioaugmentation microcosms showed also the highest biodegradation efficiencies on different total petroleum hydrocarbon fractions: saturates, aromatics, resins, asphaltene, and the highest soil heterotrophic activity as measured by accumulative evaluation of CO2.

Application of quercetin and its bio-inspired nanoparticles as anti-adhesive agents against Bacillus subtilis attachment to surface

The aim of this study was directed to reveal the repulsive effect of coated glass slides by quercetin and its bio-inspired titanium oxide and tungsten oxide nanoparticles on physical surface attachment of Bacillus subtilis as an ab-initio step of biofilm formation. Nanoparticles were successfully synthesized using sol-gel and acid precipitation methods for titanium oxide and tungsten oxide, respectively (in the absence or presence of quercetin). The anti-adhesive impact of the coated-slides was tested through the physical attachment of B. subtilis after 24h using Confocal Laser Scanning Microscopy (CLSM). Here, quercetin was presented as a bio-route for the synthesis of tungsten mixed oxides nano-plates at room temperature. In addition, quercetin had an impact on zeta potential and adsorption capacity of both bio-inspired amorphous titanium oxide and tungsten oxide nano-plates. Interestingly, our experiments indicated a contrary effect of quercetin as an anti-adhesive agent than previously reported. However, its bio-inspired metal oxide proved their repulsive efficiency. In addition, quercetin-mediated nano-tungsten and quercetin-mediated amorphous titanium showed anti-adhesive activity against B. subtilis biofilm.

Potential biodegradation of crude petroleum oil by newly isolated halotolerant microbial strains from polluted Red Sea area.

Two microbial isolates from oil polluted Red Sea water in Egypt, designated as RS-Y1 and RS-F3, were found capable of degrading Belayim mix (BX) crude oil. Strains RS-Y1 and RS-F3 were assigned to the genera Lipomyces tetrasporus and Paecilomyces variotii based on their morphological and physiological characteristics. Both isolates were compared for the biodegradation of crude petroleum-oil hydrocarbons in basal salt medium supplemented with 5% (w/v) of BX-crude oil. Gas chromatography profile showed that the biodegradation of total petroleum hydrocarbons (TPHs) inoculated with L. tetrasporus (68.3%) and P. variotii (58.15%) along with their consortium (66%) significantly reduced TPHs levels as compared to the control after 30days. L. tetrasporus (44.5%) was more effective than P. variotii strain (32.89%) in reducing the unresolved complex mixtures (UCM) content from the medium. Both isolates exhibited a strong growth over a wide range of salinity (5-45g/L NaCl).

Effect of Novel Quercetin Titanium Dioxide-Decorated Multi-Walled Carbon Nanotubes Nanocomposite on Bacillus subtilis Biofilm Development

The present work was targeted to design a surface against cell seeding and adhering of bacteria, Bacillus subtilis. A multi-walled carbon nanotube/titanium dioxide nano-power was produced via simple mixing of carbon nanotube and titanium dioxide nanoparticles during the sol-gel process followed by heat treatment. Successfully, quercetin was immobilized on the nanocomposite via physical adsorption to form a quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite. The adhesion of bacteria on the coated-slides was verified after 24 h using confocal laser-scanning microscopy. Results indicated that the quercetin/multi-walled carbon nanotube/titanium dioxide nanocomposite had more negativity and higher recovery by glass surfaces than its counterpart. Moreover, coating surfaces with the quercetin-modified nanocomposite lowered both hydrophilicity and surface-attached bacteria compared to surfaces coated with the multi-walled carbon nanotubes/titanium dioxide nanocomposite.