Produzione sostenibile di bioplastica da un nuovo ceppo cianobatterico

Climate change, fossil dependence, and plastic pollution demand circular solutions that valorize waste carbon and nutrients. This thesis develops an integrated route that couples anaerobic digestion (AD) with photosynthetic microorganisms to upgrade biogas and synthesize the biodegradable polymer poly-3-hydroxybutyrate (PHB). This work first characterizes the cyanobacterium Synechocystis sp. B12, capable of capturing CO2 and converting it into biomass and PHB, combining physiology with genomic and transcriptomic analyses to identify the molecular mechanism behind PHB accumulation. The interesting traits of Synechocystis sp. B12 make it suitable in biological biogas upgrading. Cultures tolerate high CO2 concentration in both synthetic and industrial raw biogas, selectively fixing CO2 while leaving CH4 unconsumed, enabling the upgrading of biogas into biomethane. Furthermore, Synechocystis sp. B12 converted a fraction of the captured carbon into PHB. To close nutrient loops, this work demonstrates that appropriately diluted AD digestate supports cyanobacterial growth and photosynthetic activity, positioning the liquid fraction as a circular substitute for mineral media. Finally, to address light-use bottlenecks that limit biomass productivity in industrial cultivations, this study used a high-throughput programmable fluctuating light platform for the microalga Nannochloropsis. This work investigates how non-photochemical quenching and xanthophyll-cycle kinetics (via VDE/ZEP modulation) influence growth in industrially relevant light-dark cycles. These results together delineate a CCU-based biorefinery, in which photosynthetic microorganisms upgrade biogas, recycle nutrients, and produce bioplastic, integrating waste management, renewable energy generation. This thesis also gives insights into optimizing light use in industrial cultures, aiming to accelerate the transition towards the circular economy.