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Polymeric materials made from renewable sources that can biodegrade in the environment are attracting considerable attention as substitutes for petroleum-based polymers in many fields, including additive manufacturing and, in particular, Fused Deposition Modelling (FDM). Among the others, poly(hydroxyalkanoates) (PHAs) hold significant potential as candidates for FDM since they meet the sustainability and biodegradability standards mentioned above. However, the most utilised PHA, consisting of the poly(hydroxybutyrate) (PHB) homopolymer, has a high degree of crystallinity and low thermal stability near the melting point. As a result, its application in FDM has not yet attained mainstream adoption. Introducing a monomer with higher excluded volume, such as hydroxyvalerate, in the PHB primary structure, as in poly(hydroxybutyrate-co-valerate) (PHBV) copolymers, reduces the degree of crystallinity and the melting temperature, hence improving the PHA printability. Blending amorphous poly(lactic acid) (PLA) with PHBV enhances further PHA printability via FDM. In this work, we investigated the printability of two blends characterised by different PLA and PHBV weight ratios (25:75 and 50:50), revealing the close connection between blend microstructures, melt rheology and 3D printability. For instance, the relaxation time associated with die swelling upon extrusion determines the diameter of the extruded filament, while the viscoelastic properties the range of extrusion speed available. Through thoroughly screening printing parameters such as deposition speed, nozzle diameter, flow percentage and deposition platform temperature, we determined the optimal printing conditions for the two PLA/PHBV blends. It turned out that the blend with a 50:50 weight ratio could be printed faster and with higher accuracy. Such a conclusion was validated by replicating with remarkable fidelity high-complexity objects, such as a patient's cancer-affected iliac crest model. [ABSTRACT FROM AUTHOR]

Hydrogen plays a pivotal role in the decarbonization of the fuel industry as both an energy vector and a chemical, however most of the available technologies still heavily rely on fossil fuels and sustainable processes are still unused due to their higher operational costs. MECs are devices based on the utilization of electroactive microorganisms that can interact with polarized electrodes (usually graphite-based), using them as the final electron acceptor for their metabolism. The use of a bioanode capable of oxidizing the organic substances contained in wastewater makes it possible to utilize part of the chemical energy present in the reduced waste compounds for the generation of green hydrogen, reducing the required (theoretical) potential by 85% compared to conventional electrolysis (+1.23 V vs +0.187 V). This study aims to compare two different polarization strategies of a microbial electrolysis cell aimed at hydrogen production coupled with the oxidation of synthetic wastewater. The study clearly showed the advantage of using potentiostatic polarization over galvanostatic polarization due to lower energy consumption during the potentiostatic polarization mode. Indeed, galvanostatic polarization promoted the loss of biological activity due to kinetic limitations in the biological reactions. Consequently, water oxidation on graphite granules occurred in the anodic chamber, increasing the anodic potential up to 0.95 V vs. SHE. [ABSTRACT FROM AUTHOR]

The aqueous phase produced from the hydrothermal liquefaction (HTL) of three matrices (Plasmix treated with different operative conditions and polystyrene) was subjected to acidogenic fermentation (AF) batch tests to obtain organic acids, which are the ideal substrates for biopolymers (e.g., polyhydroxyalkanoates, PHA) production from mixed microbial cultures (MMC). Parallel tests in the presence of only HTL water fractions or only glucose (an easily biodegradable compound), or in presence of both, were conducted and compared to assess any possible recalcitrant or inhibitory effect of plastic waste from the HTL treatment during the AF process. These tests resulted, within approximately 30 days of operation, in a conversion of 96 ± 21% (COD/COD) of the Plasmix by-products after a 2h thermochemical treatment into organic acids, a 54 ± 7% (COD/COD) of conversion for Plasmix by-products treated 4h, and 29 ± 1% (COD/COD) of conversion in the presence of polystyrene residual water. [ABSTRACT FROM AUTHOR]

The continuous accumulation of atmospheric CO2 requires the development of new technologies for its mitigation. Carbon capture and utilization (CCU) technologies aim to convert CO2 into precious compounds like chemicals and fuels. Biological fixation is an attractive CCU strategy in terms of cost, sustainability and variety of products. Chemoautotrophic microorganisms such as methanogens and acetogens are able to reduce CO2 into acetate and methane, respectively. Acetogens bacteria are able to use CO2 for cell growth through the Wood Liujhundal pathway, moreover, the final precursor (i.e. Acetyl-CoA) of the autotrophic metabolism, is also used in energy metabolism with acetate production as a waste product. Furthermore, it is possible to obtain multicarbon products of autotrophic origin starting from acetyl-CoA and acetate. The biotechnological use of these microorganisms requires the presence of H2 as substrate, which is used as an electron donor in the pathway. This reaction can be sustained by a biocathode in a microbial electrosynthesis cell, in which the reducing power is generated by a polarized electrode. This study proposes the use of a microbial electrosynthesis cell for conversion to acetate in H-cells by either a mixed culture enriched with Acetobacterium woodii or a pure culture of Acetobacterium woodii, to observe the difference in terms of acetate production and reducing power consumption efficiency. The mixed culture was obtained from a mixture of activated sludge and anaerobic digestate, treated by a protocol capable to select acetogenic microorganisms without the use of specific chemical inhibitors (2-Bromoethanesulfonate). Both inoculums were tested at room temperature (25°C) in the cathodic chamber of the H-cell at potentials in the range of -0.7 to -1.1 V vs SHE. The obtained results showed that the enriched mixed culture produced at -0.7 vs SHE a mixture of volatile fatty acids including C4 and C5 molecules with an overall coulombic efficiency of 50%, while at the potential of -0.9 vs SHE methane constituted the main product of the biocathode. The pure culture, on the other hand, showed a specific production of acetate with a coulombic efficiency of 44% at -0.9 vs SHE and 63% at -1.1 vs SHE. Furthermore, a drastic decrease in biocathode biomass was observed in pure culture, suggesting a higher tendency to form biofilms on the electrode unlike the mixed culture, which showed a standard growth profile in the bulk. [ABSTRACT FROM AUTHOR]