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    Investigating hydrodynamic cavitation as an efficient means for removal of per- and polyfluoroalkyl substances from solution
    (Elsevier BV, 2024-11-11) Kabiri S; Jafarian M; Navarro DA; Whitby CP; McLaughlin MJ
    With nearly five decades of per- and polyfluoroalkyl substances (PFASs) being associated with firefighting and industrial activities, these compounds inevitably accumulate in both ground and surface water. PFAS contamination in water has emerged as a significant environmental and public health concern, particularly perfluorooctanesulfonic acid (PFOS), which is often found in higher concentrations compared to other PFAS and has more pronounced adverse health effects. Addressing PFAS contamination requires treating large volumes of water, making technologies that rapidly separate and concentrate PFASs highly favoured. The strong surface activity of PFAS, such as PFOS, enables them to generate colloidal gas aphrons (CGAs) during high shear mixing of their aqueous solutions, where PFASs can be separated and collected as foam. This study aims to evaluate the effectiveness of high shear mixing in separating PFOS from solution, leveraging its accumulation at air–water interfaces. High shear-assisted PFOS separation was tested by varying parameters like rotational speed (4000 to 10,000 rpm), mixing time (30 s to 30 min), and the effect of electrolytes. Results showed greater PFOS separation in the presence of electrolytes, particularly monovalent cations like Na+, compared to divalent cations such as Ca2+, due to the creation of more stable CGAs with smaller sizes. At a mixing rate of 6000 rpm, 85 % of PFOS was removed in 30 s from a highly contaminated PFOS solution (10 mg/L), with over 95 % separation after 5 mixing cycles. While high-shear mixing was efficient in PFOS separation from highly contaminated solutions it was less efficient for low-level contaminated solutions (less than 1 mg/L). These results suggest that hydrodynamic cavitation induced by high-shear mixing seems promising for enhancing the separation of PFOS from heavily contaminated solutions. This technique could serve as a standalone method or be integrated with other PFAS removal technologies to enhance the overall efficiency of PFAS removal from polluted water sources.
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    Design of bacterial polyester beads for recombinant protein production, biomolecule separation and detection : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Microbiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2018) Du, Jinping
    Protein recovery and biomolecule detection are commonly required for scientific research as well as industrial activities. However, it is generally complicated and costly either to produce and purify recombinant proteins (especially therapeutic proteins) from engineered Escherichia coli cells, or to directly separate proteins or detect other biomolecules from natural sources. Here the PHA synthase (PhaC) mediated polyhydroxyalkanoate (PHA) bead display technology was explored as a solution to these problems by developing streamlined processes with less complex steps to achieve protein recovery and biomolecule detection. Firstly, by fusing a target protein to PhaC via a self-cleavable linker tag of either sortase (sortase A from Staphylococcus aureus) or intein (DnaB mini intein from Synechocystis sp. PCC 6803), new self-cleavable recombinant protein production and purification resins were developed. It was shown that the PhaC fusion could mediate in vivo production of PHA beads displaying the target protein. Functional target protein could be obtained at high purity from isolated PHA beads by incubation with CaCl2 and triglycine (in the case of the self-cleavable sortase tag) or by a pH shift to 6 (in the case of the self-cleavable intein tag). Six recombinant proteins were successfully produced and purified via the intein approach, including 3 model proteins (Aequorea victoria green fluorescent protein (GFP), Mycobacterium tuberculosis vaccine candidate Rv1626, and the synthetic immunoglobulin G (IgG) binding ZZ domain of protein A derived from Staphylococcus aureus) and 3 therapeutic proteins (human tumour necrosis factor alpha (TNFα), human interferon alpha-2b (IFNα2b), and human granulocyte colony-stimulating factor (G-CSF)). Of these, TNFα and IFNα2b were also successfully produced and purified via the sortase approach. Secondly, in vivo one-step production of PHA affinity resins was achieved by fusing to PhaC differently customised OBody ligands. These ligands were previously engineered by other groups from the OB-fold domain of aspartyl-tRNA synthetase (aspRS) from Pyrobactulum aerophilum, by using phage display technology, to have specific binding affinities to biomolecules of interest. The resulting recombinant OBody beads were used for lysozyme sepration from a complex substrate, and for progesterone (P4) binding. Further optimisation of the P4 binding condition is necessary before the OBody bead system can be used for P4 detection in bovine milk. However, recombinant immobilisation of OBody ligands on the surface of PHA beads expands not only the attractiveness of these emerging OBody scaffolds, but also the utility scope of PHA beads as affinity resins.
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    Milk separation and pasteurisation : the impact of separating temperature, and order of separation and pasteurisation, on the composition of skim milk, cream and separator sludge : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology of Massey University, Palmerston North, New Zealand
    (Massey University, 2014) Brooks, Evonne Hilary
    A principal purpose of the present study was to determine whether the order in which separation and pasteurisation of whole milk occurs has an effect on the composition of skim milk and cream, and thus potentially of products made using these streams. The study also sought to determine the effect of separating temperature on the composition and microbiological quality of skim milk and cream. In addition, a survey of whole milks and separator sludges at four Fonterra manufacturing sites across New Zealand was carried out to determine whether there was regional variation in minerals content. This related to the suspected involvement of sludge minerals content in the incidence of desludging port erosion found in some separators, particularly in Northland. Trials to study the effects of order of separation and pasteurisation, and of separating temperature, were first carried out in an ideal environment in the pilot plant at what is now Fonterra Research and Development Centre. Commercial-scale trials of the same kind were then carried out at Fonterra Kauri. The minerals survey was conducted by collecting and analysing whole milk and separator sludge samples collected at Fonterra Kauri, Fonterra Whareroa, Fonterra Clandeboye and Fonterra Edendale. This study has identified that dairy manufacturing plants have a larger operating window in terms of separating temperature and equipment configuration than previously thought. The ANOVA analysis may have found significant effects, but the compositional changes were minor. The mineral survey work showed that there were significant batch differences for all minerals. The calcium and phosphate contents explained most of the variability in the composition. The milk at the Kauri plant was different to milk in other parts of the country. Calcium content could be used to differentiate between the different sites tested. The phosphate content could be used to distinguish between separators.