Amjad Khalil

Fast Disinfection of Escherichia coli Bacteria Using Carbon Nanotubes Interaction with Microwave Radiation

Water disinfection has attracted the attention of scientists worldwide due to water scarcity. The most significant challenges are determining how to achieve proper disinfection without producing harmful byproducts obtained usually using conventional chemical disinfectants and developing new point-of-use methods for the removal and inactivation of waterborne pathogens. The removal of contaminants and reuse of the treated water would provide significant reductions in cost, time, liabilities, and labour to the industry and result in improved environmental stewardship. The present study demonstrates a new approach for the removal of Escherichia coli (E. coli) from water using as-produced and modified/functionalized carbon nanotubes (CNTs) with 1-octadecanol groups (C18) under the effect of microwave irradiation. Scanning/transmission electron microscopy, thermogravimetric analysis, and FTIR spectroscopy were used to characterise the morphological/structural and thermal properties of CNTs. The 1-octadecanol (C18) functional group was attached to the surface of CNTs via Fischer esterification. The produced CNTs were tested for their efficiency in destroying the pathogenic bacteria (E. coli) in water with and without the effect of microwave radiation. A low removal rate (3–5%) of (E. coli) bacteria was obtained when CNTs alone were used, indicating that CNTs did not cause bacterial cellular death. When combined with microwave radiation, the unmodified CNTs were able to remove up to 98% of bacteria from water, while a higher removal of bacteria (up to 100%) was achieved when CNTs-C18 was used under the same conditions.

Anticorrosion/antifouling properties of bacterial spore-loaded sol-gel type coating for mild steel in saline marine condition: a case of thermophilic strain of Bacillus licheniformis

This work reports the performance of a sol–gel type coating encapsulated with biofilm of inoculums of protective thermophilic strain of Bacillus licheniformis endospores isolated from the Gazan hot springs-Saudi Arabia for the inhibition of marine fouling and corrosion protection of S36-grade mild steel in 3.5 wt% NaCl medium. In order to improve its anticorrosion properties, the hybrid sol–gel coating is further doped with zinc molybdate (MOLY) and zinc aluminum polyphosphate (ZAPP) pigments. Marine fouling study was conducted at the Arabia Gulf water of Half Moon Bay, Al-Khobar, Saudi Arabia for 10 weeks on the coated samples with and without the bacterial endospores. The assessment of fouling results reveals that the bacterial endospores possess antifouling potentials since it performed better compared to its abiotic counterpart within the immersion period of study due to their foul-releasing effect. Improved corrosion and fouling resistant in the presence of the bacterial endospores could be attributed to their multi-layered hydrophobic and antibiotic coating surface after bacterial encapsulation. Spores accumulation in the sol–gel coating altered the surface wetness thereby preventing the diffusion of corrosion molecules and ions through the bulk of the coating to the metal surface; this is evident in the trend of electrochemical coating resistance and capacitance. Confocal laser scanning fluorescence and scanning electron microscopies were employed to probe bacterial viability and surface micro-cracks inherent in the coating, respectively. This is the first report of axenic thermophilic strain of Bacillus licheniformis isolated from the Arabian Gulf with inhibiting potentials against corrosion and fouling of industrial steel.

Isolation and characterization of three thermophilic bacterial strains (lipase, cellulose and amylase producers) from hot springs in Saudi Arabia

Three strains of thermophilic bacteria were isolated from two different hot springs in Saudi Arabia. These strains were designated M4 and M5 which were isolated from Al-Khoba hot spring and Sh3 which was isolated from Al-Arida hot spring. Cells are Gram positive-stain, strictly aerobic, grew optimally at pH 7.5 to 8.5 and temperature of 55 to 60°C, and tolerated maximally 10% (w/v) NaCl. The three isolates were lipase, cellulose, and amylase producers with variable degrees of enzymatic activity. They grew on various complex substrates such as yeast extract, carbohydrates and organic acids, which included starch, d-galactose, glutamate, fumarate and acetate. Microscopic observations showed that M4 had a long thick rod and spore former, M5 had a very small short rod, and Sh3 had rod and spore former. Phylogenetic analysis of 16 S rRNA sequence for the 3 strains (M4, M5 and Sh3) revealed that these strains have high sequence similarity with Bacillus sp., Brevibacillus borstelenesis and Deinococus geothermals , respectively.

Comparison of selected inhibitor doped sol–gel coating systems for protection of mild steel

Abstract Current legislation around the use of antifouling and anticorrosion coatings has increased the need to find an environment friendly alternative to existing biocide containing pretreatments for steel structures exposed to sea water. Sol–gel technology offers a solution to fouling and corrosion inhibition since sol–gel chemistry lends itself ideally to functionalisation with a variety of components, for example, corrosion inhibitors. In this study, we have utilised the above mentioned approach in order to produce an inhibitor doped sol–gel protective coating on mild steel. The corrosion protection performance of three inhibitors, i.e. SD (Shieldex303), MOLY (Moly-White101ED-PLUS) and ZAPP (Heucophos ZAPP), added individually to a sol–gel, and applied to mild steel Q panels, were evaluated using electrochemical impedance spectroscopy. The inhibitor containing coatings were shown to protect against corrosion of mild steel; the coatings containing the inhibitors Moly and ZAPP were the most effective of the systems tested. Highlights • Sol–gel coatings are potential candidate systems for the protection of mild steel substrates. • Sol–gel chemistry allows a variety of corrosion inhibitors to be incorporated into the sol–gel coating matrix. • Evaluation of corrosion inhibition efficiency of sol–gel coatings can be assessed using electrochemical impedance spectroscopy (EIS).

Probing the corrosion inhibiting role of a thermophilic Bacillus licheniformis biofilm on steel in a saline axenic culture

The growth of some bacterial biofilms has been widely reported to have defined consequences on industrial metals, and their related metabolic activities affect the overall electrochemical process of these metals in any given medium. This work seeks to unravel the role of a thermophilic Bacillus licheniformis biofilm (an isolate from the Jazan spring of Saudi Arabia) on corrosion reduction for stainless steel (316 L grade) in a saline culture medium. Grown on the steel substrate, this bacterial biofilm and the nature of its extracellular polymeric substances have been probed chemically and electrochemically for their influences on the metal dissolution within an incubation period. Corrosion inhibition in the presence of varying concentrations (in CFU ml−1) of this bacterium in the biotic-inoculate systems is explained in terms of corrosion resistance and capacitance of the biofilm. The corrosion rate of steel is found to reduce significantly in the saline culture medium within the range of concentrations of bacterium under study compared with the sterile control. This is attributed to the adhesion of a relatively compact and dense “beneficial” biofilm as well as the secretion of corrosion inhibiting substances from the bacterial biofilm as revealed during surface analysis.

Laser-induced photocatalytic inactivation of coliform bacteria from water using pd-loaded nano-WO3

Abstract Nano palladium-loaded on nano tungsten trioxide ( n -Pd/ n -WO 3 ), with 10% wt Pd loading, was prepared by the impregnation evaporation method. The n -WO 3 support was prepared by dehydration of tungstic acid (H 2 WO 4 ). The n -Pd/ n -WO 3 was characterized by Raman spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). This material was tested as a photocatalyst for inactivation and killing of coliform bacteria, by applying 355-nm pulsed UV laser radiations, generated from the third harmonic of Nd:YAG laser, to a model water sample, prepared using bacteria strains of Escherichia coli . The killing effect of n -Pd/ n - WO 3 on coliform bacteria was characterized by means of selective culture media. The photocatalysis process did result in a very high irreversible injury (99%) under investigated conditions. This process is cost-effective because no bacteria re-growth was recorded under optimum environment conditions. The disinfection rate of water was estimated by exponential decay. The conventional titania (TiO 2 ) semiconductor and commercially available WO 3 display a lower decay rate than that for n -Pd/ n -WO 3 .

Genome Sequence of Anoxybacillus flavithermus Strain AK1, a Thermophile Isolated from a Hot Spring in Saudi Arabia

ABSTRACT Anoxybacillus flavithermus strain AK1 was isolated from Al-Ain Alhara, a thermal hot spring located 50 km southeast of the city of Gazan, Saudi Arabia (16°56ʹN, 43°15ʹE). The sequenced and annotated genome is 2,630,664 bp and encodes 2,799 genes.

Photo-catalytic deactivation of sulfate reducing bacteria – a comparative study with different catalysts and the preeminence of Pd-loaded WO3 nanoparticles

Sulfate reducing bacteria (SRB), predominantly present in the produced water in oil fields is known for being an agent for degrading the quality of crude oil by introducing an elevated level of sulfur content, initiating oil souring and corroding the oil pipelines. In addition, this bacterium poses an immense health threat to the oil field workers due to the generation of radioactive barium sulfide. Photo-catalytic deactivation of the sulfate reducing bacteria in water with four different pure and palladium loaded photo-catalysts was carried out and their relative efficiencies are compared. It was found that n-Pd/WO3 at an optimum concentration, in conjunction with 355 nm pulsed laser radiation showed a substantial increase in the photo-catalytic deactivation of SRB in contaminated water. A 110 fold increase in the SRB deactivation rate, compared to UV radiation (in the absence of catalyst) and a 30 fold increase in the same, compared to pure WO3, and the bench mark catalyst (TiO2) under the same experimental conditions was observed. All the nano-structured photo-catalysts were synthesized, optically and morphologically characterized to optimize the function of each catalyst effective in the deactivation of harmful sulfate-reducing bacteria in water.

Novel Antimicrobial Polyelectrolytes Nanofilm Coatings Using the Layer By Layer Technique~!2008-08-26~!2008-10-09~!2008-11-26~!

A novel method using the layer by layer (LBL) technique was investigated to deposit polyelectrolytes with an- tibacterial properties. A glass substrate was coated by a cationic biguanide followed by the anionic polystyrene sulfonate until a total of twenty layers were deposited. The layers thickness was measured by ellipsometry and the surface morphol- ogy was scanned by an atomic force microscope. The layers thickness reached 60nm. The coated and uncoated glass was immersed into tubes containing a nutrient broth media inoculated with Proteus sp., (a gram negative , rod, glucose fer- menting bacteria) in a concentration of (~10 5 cells/mL) and incubated at 37°C for 24 hours. The SEM (Scanning Electron Microscope) micrographs showed a significant reduction in the settlement of Proteus sp. Colonies on the glass coated with polyelectrolytes.

Nano-NiO as a photocatalyst in antimicrobial activity of infected water using laser induced photo-catalysis

Nano NiO photo catalyst was synthesized by sol gel method and it is used as a photo catalyst in conjunction with 355 nm laser radiation in the process of disinfecting water infected with Escherichia coli microorganism. When synthesized nano-NiO material is used as a photo catalyst, a bacteria decay rate constant of 0.35 min-1 and this rate constant is higher than the bacteria decay rate constant of 0.24 minutes−1 for TiO2 as a photo catalyst under same catalytic concentration and laser pulse energy. From the TEM study, a grain size as low as 20–40 nm was observed and the absorption study showed a band gap of 3.85 eV. The dependence of depletion rate of bacterial count in the infected water on the nano-NiO concentration and the irradiating laser pulse energy were carried out.