Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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    Extracellular polymeric substances- the real target in eradicating pseudomonad biofilms
    (Elsevier Ltd, 2025-09-01) Muthuraman S; Palmer J; Flint S
    Pseudomonads are common psychrotrophic spoilage bacteria associated with dairy, poultry, and meat processing environments. Pseudomonads can form robust biofilms at cold temperatures and produce thermostable spoilage enzymes. This review discusses the biofilm formation aspects of pseudomonads, such as biofilm formation at the air-liquid interface, psychrotrophic temperatures, and distinct EPS production. The components of the EPS produced by pseudomonads and the potential of pseudomonads as a public good provider to other bacteria within the biofilm are highlighted. The elimination strategies available, other than conventional CIP methods, were discussed. The elimination strategies either target the cells or the EPS. When the cells were removed completely, the remaining EPS footprints encouraged the robust regrowth of the biofilms and strategies targeting only the EPS, such as enzymes, led to multiple colonisation possibilities from the dispersed aggregates. Combining the cell and EPS targeting strategies would result in complete biofilm removal. However, the cost-effective production, rapid removal and safety on food matrices need to be considered while designing the control strategies of pseudomonad biofilm removal.
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    Surface Chemical Characterisation of Pyrite Exposed to Acidithiobacillus ferrooxidans and Associated Extracellular Polymeric Substances
    (MDPI (Basel, Switzerland), 2018-04-01) La Vars SM; Newton K; Quinton JS; Cheng P-Y; Wei D-H; Chan Y-L; Harmer SL
    A. ferrooxidans and their metabolic products have previously been explored as a viable alternative depressant of pyrite for froth flotation; however, the mechanism by which separation is achieved is not completely understood. Scanning electron microscopy (SEM), photoemission electron microscopy (PEEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and captive bubble contact angle measurements have been used to examine the surface physicochemical properties of pyrite upon exposure to A. ferrooxidans grown in HH medium at pH 1.8. C K-edge near edge X-ray absorption fine structure (NEXAFS) spectra collected from PEEM images indicate hydrophilic lipids, fatty acids and biopolymers are formed at the mineral surface during early exposure. After 168 h, the spectra indicate a shift towards protein and DNA, corresponding to an increase in cell population and biofilm formation on the surface, as observed by SEM. The Fe L-edge NEXAFS show gradual oxidation of the mineral surface from Fe(II) sulfide to Fe(III) oxyhydroxides. The oxidation of the iron species at the pyrite surface is accelerated in the presence of A. ferrooxidans and extracellular polymeric substances (EPS) as compared to HH medium controls. The surface chemical changes induced by the interaction with A. ferrooxidans show a significant decrease in surface hydrophobicity within the first 2 h of exposure. The implications of these findings are the potential use of EPS produced during early attachment of A. ferrooxidans, as a depressant for bioflotation.