Effects of environmental conditions on the quality and physico-chemical properties of bio-produced polyhydroxyalkanoates (PHAs)Jovanovski, Terezija (Avtor) Dogša, Iztok (Mentor) Werker, Alan (Komentor) polyhydroxyalkanoatesbiopolymersdegradationthermogravimetric analysisdifferential scanning calorimetryImpacts of selected environmental conditions on the quality and quantity of polyhydroxyalkanoates (PHAs) produced with surplus activated sludge were studied. The effects on the PHA-rich biomass were measured immediately after the pH adjustments in the range from pH 2 to pH 12, and after a 48-h anaerobic incubation at 55 °C without prior PHA extraction from biomass. For comparison, two control samples at native pH, incubated at 55 °C and 25 °C, were studied. Methods applied involved quantification of the PHA by thermogravimetric analysis (TGA) together with volatile suspended solids (VSS) or chemical oxygen demand (COD) analysis. Degradation products were measured by ion chromatography (IC) or ultra-high-pressure liquid chromatography (UHPLC). PHA thermal decomposition behaviour and typical phase transitions were analysed by TGA and differential scanning calorimetry (DSC), respectively. Results show that PHA properties (quantity and quality) were best preserved at pH 2. Other conditions revealed different degrees of PHA degradation, where neutral, alkaline conditions and incubation at 25 °C were the most detrimental, especially after 48 h of incubation – a PHA concentration decrease of up to (56 ± 5)% was observed. The acidification of samples before the measurements improved their thermal stability. The observed decrease of measurable PHA mass at pH > 2 was accompanied by the changes in thermal properties (melting, crystallization, glass transition) that were indicative of decreased stability or integrity of PHA and can be explained by a decrease in the molecular weight of PHA.[T. Jovanovski]20222022-02-19 07:15:02Magistrsko delo/naloga135065sl