Browsing by Author "Johnston, Brian"

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    Biomass extraction using non-chlorinated solvents for biocompatibility improvement of polyhydroxyalkanoates
    (MDPI, 2018-07-03) Jiang, Guozhan; Johnston, Brian; Townrow, David E.; Radecka, Iza; Koller, Martin; Chaber, Paweł; Adamus, Grażyna; Kowalczuk, Marek
    An economically viable method to extract polyhydroxyalkanoates (PHAs) from cells is desirable for this biodegradable polymer of potential biomedical applications. In this work, two non-chlorinated solvents, cyclohexanone and γ-butyrolactone, were examined for extracting PHA produced by the bacterial strain Cupriavidus necator H16 cultivated on vegetable oil as a sole carbon source. The PHA produced was determined as a poly(3-hydroxybutyrate) (PHB) homopolyester. The extraction kinetics of the two solvents was determined using gel permeation chromatography (GPC). When cyclohexanone was used as the extraction solvent at 120 °C in 3 min, 95% of the PHB was recovered from the cells with a similar purity to that extracted using chloroform. With a decrease in temperature, the recovery yield decreased. At the same temperatures, the recovery yield of γ-butyrolactone was significantly lower. The effect of the two solvents on the quality of the extracted PHB was also examined using GPC and elemental analysis. The molar mass and dispersity of the obtained polymer were similar to that extracted using chloroform, while the nitrogen content of the PHB extracted using the two new solvents was slightly higher. In a nutshell, cyclohexanone in particular was identified as an expedient candidate to efficiently drive novel, sustainable PHA extraction processes.
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    A comparative study of three-dimensional printing directions: The degradation and toxicological profile of a PLA/PHA blend
    (Elsevier, 2018-04-17) Gonzalez Ausejo, Jennifer; Rydz, Joanna; Musioł, Marta; Sikorska, Wanda; Sobota, Michał; Włodarczyk, Jakub; Adamus, Grażyna; Janeczek, Henryk; Kwiecień, Iwona; Hercog, Anna; Johnston, Brian; Khan, Habib R.; Kannappan, Vinodh; Jones, Keith R.; Morris, Mark R.; Jiang, Gouzhan; Radecka, Iza; Kowalczuk, Marek
    The use of biobased plastics is of great importance for many applications. Blending thermoplastic polylactide (PLA) with polyhydroxyalkanoate (PHA) enables the formulation of a more mechanically powerful material and this enables tailored biodegradation properties. In this study we demonstrate the 3D printing of a PLA/PHA blend as a potential candidate for biocompatible material applications. The filament for 3D printing consisted of PHA, which contains predominantly 3-hydroxybutyrate units and a small amount of 3-hydroxyvalerate units, as revealed by multistage mass spectrometry (ESI-MSn). This research found that the properties of 3D printed species before and during abiotic degradation are dependent on printing orientation. Furthermore, the 3D printed specimens exhibited good biocompatibility with HEK293 cells, indicating real promise as biological scaffolds for tissue engineering applications.