This study evaluates a biorefinery concept for producing poly(3-hydroxybutyrate) (PHB) with the cyanobacterial strain Synechocystis salina. Due to this reason, pigment extraction and cell disruption were investigated as pre-treatment steps for the harvested cyanobacterial biomass. The results demonstrated that at least pigment removal was necessary to obtain PHB with processable quality (weight average molecular weight: 569-988kgmol-1, melting temperature: 177-182°C), which was comparable to heterotrophically produced PHB. The removed pigments could be utilised as additional by-products (chlorophylls 0.27-1.98mgg-1 TS, carotenoids 0.21-1.51mgg-1 TS, phycocyanin 0-127mgg-1 TS), whose concentration depended on the used nutrient source. Since the residual biomass still contained proteins (242mgg-1 TS), carbohydrates (6.1mgg-1 TS) and lipids (14mgg-1 TS), it could be used as animal feed or converted to biomethane (348 mn3 t-1VS) and fertiliser. The obtained results indicate that the combination of photoautotrophic PHB production with pigment extraction and utilisation of residual biomass offer the highest potential, since it contributes to decrease the environmental footprint of the process and because biomass could be used in a cascading way and the nutrient cycle could be closed.

Graz University of Technology Institute for Chemistry and Technology of Materials Stremayrgasse 9 8010 Graz Austria

Graz University of Technology Institute for Chemistry and Technology of Materials Stremayrgasse 9 8010 Graz Austria; Brno University of Technology Faculty of Chemistry Department of Food Chemistry and Biotechnology Purkyňova 118 612 00 Brno Czech Republic

University of Natural Resources and Life Sciences Vienna Department of Agrobiotechnology IFA Tulln Konrad Lorenz Straße 20 3430 Tulln Austria

University of Natural Resources and Life Sciences Vienna Department of Agrobiotechnology IFA Tulln Konrad Lorenz Straße 20 3430 Tulln Austria; BIOENERGY2020 GmbH Bioconversion and Biogas Systems Tulln Research Site Konrad Lorenz Straße 20 3430 Tulln Austria

University of Natural Resources and Life Sciences Vienna Department of Agrobiotechnology IFA Tulln Konrad Lorenz Straße 20 3430 Tulln Austria; BIOENERGY2020 GmbH Bioconversion and Biogas Systems Tulln Research Site Konrad Lorenz Straße 20 3430 Tulln Austria; Institute of Environment and Food Security Montfortstraße 4 6900 Bregenz Austria

University of Natural Resources and Life Sciences Vienna Department of Agrobiotechnology IFA Tulln Konrad Lorenz Straße 20 3430 Tulln Austria; ROHKRAFTgreen OG Schulgasse 6 3454 Reidling Austria

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Biotechnological Production of Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate-co-3-Hydroxyvalerate) Terpolymer by Cupriavidus sp. DSM 19379