Research Doctoral Student, University of Aberdeen
Evaluate interactions of exopolymeric substances exuded by certain marine bacterial isolates.
To evaluate interactions of exopolymeric substances and possible required cost-effective specialty chemical additives tailored to provide optimal well drilling, completion and intervention services due to rheological properties of exopolymeric substances produced by certain bacterial strains to serve as oilfield chemical to enhance effective drilling.
Generally, rheological properties of bacterial exopolysaccharides is one of its kind due to high purity and regular structure. Some unique bacterial strains produce a large diversity of exopolymers that enhance adaptation, with extreme environment. Some reduces interfacial tension barriers, thus making it applicable as thickeners, emulsifiers, and suspending agents in food, dairy product, pharmaceutical and petroleum industries. A classical polymer known as xanthan gum produced as microbial exopolysaccharide by gram-negative bacterium known as Xanthonomas campestris, it employs fermentation of simple and complex sugars such as glucose, sucrose, or other carbohydrate sources. Biopolymers are applied in food production, manufacturing pharmaceutical, cosmetic and petrochemical industrial application as thickeners, stabilizer, or agent of emulsification when mixed with gelling potentials. Xanthonomas campestris produces exopolymeric substances composed of repeated units of pentasaccharides of two glucose, two mannose and one glucoronic acid residues as its primary structure. It is expected that a patent on the exopolymeric substances produced by bacterial strains will be developed for industrial application and of economic and environmental importance. I am so passionate about utilization/transformation of basic biomaterials into finished goods so as to satisfy human want and also create a household brand.
Abstract: The vast majority of systemic bacterial infections are caused by facultative, often antibiotic-resistant, pathogens colonizing human body surfaces. Nasal carriage of Staphylococcus aureus predisposes to invasive infection, but the mechanisms that permit or interfere with pathogen colonization are largely unknown. Whereas soil microbes are known to compete by production of antibiotics, such processes have rarely been reported for human microbiota. We show that nasal Staphylococcus lugdunensis strains produce lugdunin, a novel thiazolidine-containing cyclic peptide antibiotic that prohibits colonization by S. aureus, and a rare example of a non-ribosomally synthesized bioactive compound from human-associated bacteria. Lugdunin is bactericidal against major pathogens, effective in animal models, and not prone to causing development of resistance in S. aureus. Notably, human nasal colonization by S. lugdunensis was associated with a significantly reduced S. aureus carriage rate, suggesting that lugdunin or lugdunin-producing commensal bacteria could be valuable for preventing staphylococcal infections. Moreover, human microbiota should be considered as a source for new antibiotics.
Pub.: 27 Jul '16, Pinned: 25 Aug '17
Abstract: Membrane filtration has been widely applied for water treatment, wastewater reclamation and seawater desalination. Although extensive research work has been conducted to better understand the fouling mechanism under various conditions, little has been known about the transparent exopolymer particles (TEP)-associated membrane fouling at different Na(+) concentrations. In this study, the influence of Na(+) concentration on the TEP formation as well as the filtration behaviors of alginate blocks was investigated. Results showed that increasing Na(+) concentration substantially reduced the TEP formation from all types of alginate blocks, thus preventing the cake layer development on the membrane surface. As a result, the TEP-associated membrane fouling was found to be kinetically slower and much less at higher Na(+) level. Furthermore, filtration tests of alginate blocks at freshwater and seawater conditions were also conducted, showing that TEP-associated fouling in freshwater is much server than that in seawater at the defined conditions. This study reveals that the TEP formation is significantly influenced by the chemistry condition of bulk solution and membrane fouling is profoundly affected by the TEP levels in feed water.
Pub.: 04 Jan '17, Pinned: 19 Aug '17
Abstract: The characterisation and flocculation behaviour of exopolymer R-202 produced by Rhodococcus rhodochrous were investigated. The water-soluble fraction of this polymer with the molecular weight of about 1.3 × 103 kDa was found to be 62.86% of polysaccharide and 10.36% of protein. Chemical analysis showed the presence of reducing sugars, uronic acids, and amino sugars at the concentrations of 232.41 μg/mg, 45.29 μg/mg and 15.07 μg/mg, respectively. The HPLC analysis revealed that the monosaccharide components of the studied exopolymer were mannose, glucose and galactose at the molar ratio of 12:6:1. The flocculating activity was measured using the kaolin suspension and the basic flocculation parameters of exopolymer were established. The highest flocculating activity of exopolymer R-202 was observed at a dosage of 2 mg/L, a pH value 7.2 and in the presence of 10 mM solutions of salts (NaCl, CaCl2, MgCl2 or FeCl2). This effect depended on the type of ions and increased in the order - Na+ < Ca2+ < Mg2+ < Fe2+. The highest flocculating activity appeared in the presence of Fe2+ ions. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) showed that R-202 is a negatively charged polymer and contains functional groups (hydroxyl, carboxyl, amine, amide) preferred for the flocculation process.
Pub.: 10 Jan '17, Pinned: 19 Aug '17
Abstract: Leptothrix species, aquatic Fe-oxidizing bacteria, excrete nano-scaled exopolymer fibrils. Once excreted, the fibrils weave together and coalesce to form extracellular, microtubular, immature sheaths encasing catenulate cells of Leptothrix. The immature sheaths, composed of aggregated nanofibrils with a homogeneous-looking matrix, attract and bind aqueous-phase inorganics, especially Fe, P, and Si, to form seemingly solid, mature sheaths of a hybrid organic-inorganic nature. To verify our assumption that the organic skeleton of the sheaths might sorb a broad range of other metallic and nonmetallic elements, we examined the sorption potential of chemically and enzymatically prepared protein-free organic sheath remnants for 47 available elements. The sheath remnants were found by XRF to sorb each of the 47 elements, although their sorption degree varied among the elements: >35% atomic percentages for Ti, Y, Zr, Ru, Rh, Ag, and Au. Electron microscopy, energy dispersive x-ray spectroscopy, electron and x-ray diffractions, and Fourier transform infrared spectroscopy analyses of sheath remnants that had sorbed Ag, Cu, and Pt revealed that (i) the sheath remnants comprised a 5-10 nm thick aggregation of fibrils, (ii) the test elements were distributed almost homogeneously throughout the fibrillar aggregate, (iii) the nanofibril matrix sorbing the elements was nearly amorphous, and (iv) these elements plausibly were bound to the matrix by ionic binding, especially via OH. The present results show that the constitutive protein-free exopolymer nanofibrils of the sheaths can contribute to creating novel filtering materials for recovering and recycling useful and/or hazardous elements from the environment.
Pub.: 10 Jun '17, Pinned: 19 Aug '17