Suchergebnisse

1 p. ; Biopolymers such as polyhydroxyalkanoates (PHAs) are considered as an alternative to conventional plastics, but their production can only be economically feasible by waste valorization approaches. The project Afterlife1, funded by the Bio-Based Industries Joint Undertaking under the European Union's Horizon 2020 research and innovation program, aims a flexible, cost- and resource-efficient process for recovering and valorizing the relevant fractions from wastewater (WW). The AFTERLIFE process will isolate the different components of value using a cascade of membrane filtration units that will separate all the solids in the WW. These will then be treated to obtain highly-pure extracts and metabolites or, alternatively, to be converted into PHA. Volatile fatty acid (VFA) fractions with different compositions were obtained by the acidogenic fermentation of the WW from three food industries. In this study, we present a strategy to revalorize those VFAs for the production of PHA using pure cultures. The model strain Cupriavidus necator H16 is a non-pathogenic bacterium that has been the subject of intensive research due to its metabolical versatility and its ability to store up to 90 % of its cell dry weight as polyhydroxybutyrate (PHB). The tolerance studies of H16 strain to VFAs and the determination of key physiological parameters have been applied to optimize the fermentation conditions using three fermented industrial WW on a lab-scale up to 5 liters. The highest PHA concentration (5 g L-1 ), PHA productivity (0.1 g L-1 h-1), and PHA content (80 %) have been achieved by modulating the carbon pulses in a fed-batch system, based on the specific consumption and biomass/product produced. 1https://www.bbi.europa.eu/projects/afterlife. ; Peer reviewed

16 p.-5 fig.-6 tab. ; Background: Rhodospirillum rubrum is a purple non-sulphur bacterium that produces H2 by photofermentation of several organic compounds or by water gas-shift reaction during CO fermentation. Successful strategies for both processes have been developed in light-dependent systems. This work explores a dark fermentation bioprocess for H2 production from water using CO as the electron donor. ; Results: The study of the influence of the stirring and the initial CO partial pressure (pCO) demonstrated that the process was inhibited at pCO of 1.00 atm. Optimal pCO value was established in 0.60 atm. CO dose adaptation to bacterial growth in fed-batch fermentations increased the global rate of H2 production, yielding 27.2 mmol H2 l−1 h−1 and reduced by 50% the operation time. A kinetic model was proposed to describe the evolution of the molecular species involved in gas and liquid phases in a wide range of pCO conditions from 0.10 to 1.00 atm. ; Conclusions: Dark fermentation in R. rubrum expands the ways to produce biohydrogen from CO. This work optimizes this bioprocess at lab-bioreactor scale studying the influence of the stirring speed, the initial CO partial pressure and the operation in batch and fed-batch regimes. Dynamic CO supply adapted to the biomass growth enhances the productivity reached in darkness by other strategies described in the literature, being similar to that obtained under light continuous syngas fermentations. The kinetic model proposed describes all the conditions tested. ; The European Union's Horizon 2020 research and innovation program under grant agreement no. 679050 (CELBICON), the Community of Madrid (P2018/NMT4389) and the Spanish Ministry of Science, Innovation and Universities (BIO2017-83448-R) supported this work. ; Peer reviewed