Geoff Robson

Publications (98) View all

• Article: Effect of biostimulation and bioaugmentation on degradation of polyurethane buried in soil.

  L Cosgrove, P L McGeechan, P S Handley, G D Robson
  [show abstract] [hide abstract]
  ABSTRACT: This work investigated biostimulation and bioaugmentation as strategies for removing polyurethane (PU) waste in soil. Soil microcosms were biostimulated with the PU dispersion agent "Impranil" and/or yeast extract or were bioaugmented with PU-degrading fungi, and the degradation of subsequently buried PU was determined. Fungal communities in the soil and colonizing buried PU were enumerated on solid media and were analyzed using denaturing gradient gel electrophoresis (DGGE). Biostimulation with yeast extract alone or in conjunction with Impranil increased PU degradation 62% compared to the degradation in untreated control soil and was associated with a 45% increase in putative PU degraders colonizing PU. Specific fungi were enriched in soil following biostimulation; however, few of these fungi colonized the surface of buried PU. Fungi used for soil bioaugmentation were cultivated on the surface of sterile wheat to form a mycelium-rich inoculum. Wheat, when added alone to soil, increased PU degradation by 28%, suggesting that wheat biomass had a biostimulating effect. Addition of wheat colonized with Nectria haematococca, Penicillium viridicatum, Penicillium ochrochloron, or an unidentified Mucormycotina sp. increased PU degradation a further 30 to 70%, suggesting that biostimulation and bioaugmentation were operating in concert to enhance PU degradation. Interestingly, few of the inoculated fungi could be detected by DGGE in the soil or on the surface of the PU 4 weeks after inoculation. Bioaugmentation did, however, increase the numbers of indigenous PU-degrading fungi and caused an inoculum-dependent change in the composition of the native fungal populations, which may explain the increased degradation observed. These results demonstrate that both biostimulation and bioaugmentation may be viable tools for the remediation of environments contaminated with polyurethane waste.
  Applied and environmental microbiology 11/2009; 76(3):810-9. · 3.69 Impact Factor
• Article: An investigation of anthraquinone dye biodegradation by immobilized Aspergillus flavus in fluidized bed bioreactor.

  Saadia Andleeb, Naima Atiq, Geoff D Robson, Safia Ahmed
  [show abstract] [hide abstract]
  ABSTRACT: Biodegradation and biodecolorization of Drimarene blue K(2)RL (anthraquinone) dye by a fungal isolate Aspergillus flavus SA2 was studied in lab-scale immobilized fluidized bed bioreactor (FBR) system. Fungus was immobilized on 0.2-mm sand particles. The reactor operation was carried out at room temperature and pH 5.0 in continuous flow mode with increasing concentrations (50, 100, 150, 200, 300, 500 mg l(-1)) of dye in simulated textile effluent on the 1st, 2nd, 5th, 8th, 11th, and 14th days. The reactors were run on fill, react, settle, and draw mode, with hydraulic retention time (HRT) of 24-72 h. Total run time for reactor operation was 17 days. The average overall biological oxygen demand (BOD), chemical oxygen demand (COD), and color removal in the FBR system were up to 85.57%, 84.70%, and 71.3%, respectively, with 50-mg l(-1) initial dye concentration and HRT of 24 h. Reductions in BOD and COD levels along with color removal proved that the mechanism of biodecolorization and biodegradation occurred simultaneously. HPLC and LC-MS analysis identified phthalic acid, benzoic acid, 1, 4-dihydroxyanthraquinone, 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedione, and catechol as degradation products of Drimarene blue K(2)RL dye. Phytotoxicity analysis of bioreactor treatments provided evidence for the production of less toxic metabolites in comparison to the parent dye. The present fluidized bed bioreactor setup with indigenously isolated fungal strain in its immobilized form is efficiently able to convert the parent toxic dye into less toxic by-products.
  Environmental Science and Pollution Research 12/2011; 19(5):1728-37. · 2.65 Impact Factor
• Article: Interrogation of related clinical pan-azole-resistant Aspergillus fumigatus strains: G138C, Y431C, and G434C single nucleotide polymorphisms in cyp51A, upregulation of cyp51A, and integration and activation of transposon Atf1 in the cyp51A promoter.

  Ahmed M Albarrag, Michael J Anderson, Susan J Howard, Geoff D Robson, Peter A Warn, Dominique Sanglard, David W Denning
  [show abstract] [hide abstract]
  ABSTRACT: Multiple Aspergillus fumigatus isolates from a patient with two aspergillomas complicating chronic pulmonary aspergillosis were pan-azole resistant. Microsatellite typing was identical for all isolates despite major phenotypic and some growth rate differences. Three different cyp51A mutations were found (G138C, Y431C, and G434C), of which the first two were demonstrated by heterologous expression in a hypersusceptible Saccharomyces cerevisiae strain to be at least partly responsible for elevated MICs. cyp51A and cyp51B gene duplication was excluded, but increased expression of cyp51A was demonstrated in three isolates selected for additional study (7-to 13-fold increases). In the isolate with the greatest cyp51A expression, an Aft1 transposon was found inserted 370 bp upstream of the start codon of the cyp51A gene, an integration location never previously demonstrated in Aspergillus. Two transcription start sites were identified at 49 and 136 bp upstream of the start codon. The role of the Aft1 transposon, if any, in modulating cyp51A expression remains to be established. Increased mRNA expression of the transporters AfuMDR1 and AfuMDR4 also was demonstrated in some isolates, which could contribute to azole resistance or simply represent a stress response. The diversity of confirmed and possible azole resistance mechanisms demonstrated in a single series of isogenic isolates is remarkable, indicating the ability of A. fumigatus to adapt in the clinical setting.
  Antimicrobial Agents and Chemotherapy 08/2011; 55(11):5113-21. · 4.84 Impact Factor
• Article: An HPLC method development for the assessment of degradation products of anthraquinone dye.

  Saadia Andleeb, Naima Atiq, Arvind Parmar, Geoff D Robson, Safia Ahmed
  [show abstract] [hide abstract]
  ABSTRACT: This paper describes the development of a simple and sensitive method with reduced run time for the estimation of biodegradation product of an anthraquinone dye, Drimarene blue K(2)RL. The chromatographic analysis was performed using a reversed-phase high performance liquid chromatography (HPLC) with a Lichrospher® RP-18 column, 5 μm particle size, 25 cm × 4.6 mm internal diameter using a 70:20:10 (v/v) mixture of acetonitrile-ammonium acetate buffer (0.02 M) with 0.8% Trifluoroacetic acid (pH 2.5) and methanol as eluent. Flow rate was adjusted to 1.2 mL min(-1). The metabolites (phthalic acid, benzoic acid, 1, 4-dihydroxyanthraquinone, and 2,3-dihydro-9,10-dihydroxy-1,4-anthracenedione) were identified by running HPLC grade standards in defined concentrations. The retention time of the compounds were 2.0, 2.5, 5.2, and 7.2 min for phthalic acid, benzoic acid, 1, 4-dihydroxyanthraquinone, and 2,3-dihydro- 9,10-dihydroxy-1,4-anthracenedione, respectively. The reliability, sensitivity, and validation of the method were checked by calculating recoveries of the individual compounds in the acetonitrile and dye degradation media. The lower limits of detection for anthraquinone metabolites and the separation of acid and anthraquinone metabolites in short time were achieved.
  Environmental Monitoring and Assessment 05/2011; 176(1-4):597-604. · 1.40 Impact Factor
• Article: Influence of starvation, surface attachment and biofilm growth on the biocide susceptibility of the biodeteriogenic yeast Aureobasidium pullulans.

  H A Sabev, G D Robson, P S Handley
  [show abstract] [hide abstract]
  ABSTRACT: To investigate the effect of starvation, surface attachment and growth in a biofilm on the susceptibility of Aureobasidium pullulans to the biocides 2-n-octyl-4-isothiazolin-3-one (OIT) and sodium hypochlorite (NaOCl). Fluorescence loss from a green fluorescent protein (GFP)-transformed strain was used to monitor real-time loss in viability as previously described in situ in 96-well plates. Exponential phase, yeast-like (YL) cells were settled in the bottom of the wells as a low-density monolayer (LDM) and were susceptible to all biocide concentrations (25-100 mug ml(-1)). The exponential phase YL cells were either starved for 48 h in suspension or starved for 48 h as LDMs in the wells. Starvation in both cases led to a small reduction in susceptibility to the biocides. In contrast, 48-h biofilms grown in malt extract broth showed an apparent lack of susceptibility to 25 and 50 mug ml(-1) OIT and to 25-100 mug ml(-1) NaOCl. However, when the OIT concentration was increased to compensate for the higher cell density in the biofilm, the biofilms were found to be equally susceptible to the LDM. Starvation of A. pullulans YL cells either in suspension or as attached LDM resulted in a decrease in susceptibility to low concentrations of both OIT and NaOCl while the apparent reduced susceptibility of mature biofilms was due to the increase in biofilm cell density rather than true biofilm resistance per se. Monitoring fluorescence loss from the GFP-transformed strain of A. pullulans can be used as a fast and reliable method for monitoring cell death in real time as a response to biocide and antimicrobial challenge.
  Journal of Applied Microbiology 09/2006; 101(2):319-30. · 2.34 Impact Factor