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Acid soluble biopolymeric substances (SBP) were isolated from different urban biowastes comprised of a range of materials available from metropolitan areas. These biowastes provided products with a chemical nature and solubility properties changing over a wide range and, thus, allowed to assess the effect of the variability of the chemical nature on molecular conformation and surface activity in water solution. For this scope, the SBP were characterized for chemical composition and molecular weight (MW) by microanalysis, potentiometric titration, (13)C NMR spectroscopy, and size exclusion chromatography (SEC) coupled with an online multiangle light scattering (MALS) detector. These materials were found to have 67-463 kg mol(-1) MW and 6-53 polydispersity index and to contain carboxylic acid and phenol groups bonded to aromatic and aliphatic C chains. An empirical parameter (LH) was calculated for use as an index of the lipophilic/hydrophilic C atoms ratio. The products solubility properties in solvents of different polarity, surface activity, power to enhance the water solubility of hydrophobic compounds, and particle size in water solution were also investigated by measurements of the products partition coefficient between polyethylene glycol and water (KPEGW) and of air-water surface tension (γ), water-hexane interfacial tension (IFT), disperse red orange dye solubility (DS), and dynamic light scattering (DLS) versus added SBP concentration (Cs). The results indicate that LH correlates well with KPEGW and with the products surface activity properties. Both γ and DS are shown to depend on Cs, although in opposite ways, that is, higher Cs values yield lower γ and higher DS values. Both DS-Cs and γ-Cs plots showed a significant slope change at approximately the same 1.8-2.5 g L(-1) Cs value. This suggested a change of molecular conformation taking place at the above Cs values. Hydrodynamic diameter values for SBP in solution at Cs ≤ 10 g L(-1) were found to range from 130 to 300 nm, consistent with their macromolecular nature. The DLS coupled to the γ data were consistent with molecules at the water-air interphase and in the bulk water phase having different conformations, but not significantly different molecular sizes. Molecular aggregates more likely form at 50-100 g L(-1) Cs. The results confirm that urban biowastes are a sustainable source of biobased products that may have real commercial perspectives.

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Objectives of this study were to investigate urban biowastes as sustainable source of soluble biobased products (SBO) for use in animal diet and, possibly, to assess product chemical nature-performance relationships. Thus, five different materials sourced from biowastes processed by anaerobic and/or aerobic fermentation were treated to yield five different SBO. The products were first characterized for their chemical nature. Afterwards, they were tested as diet supplements to modulate pig's cecal fermentation of a protein feed. In vitro fermentation of the protein feed was performed using the cecal content collected from slaughtered pigs as incubation liquor. The experimental plan comprised 29 treatments distributed over the 5 SBO used at 5-6 doses each in the 0.1-1.4% concentration range, compared to a SBO free control. During the 24 h in vitro fermentation, gas and liquor samples were analyzed for total gas volume vs. time production, and for ammonia and volatile fatty acids concentration. The results showed the investigated SBO to be significantly different for both their chemical composition and in their effects on the measured fermentation indicators. All materials showed significant effects already at the lowest 0.1% concentration. However the SBO isolated from composted residues decreased ammonia production, whereas the SBO isolated from the digestate of the food residues' anaerobic treatment had the opposite effect. Ammonia production was found to be directly correlated with isobutyric and isovaleric production. The results clearly pointed out reduced proteolysis and N mineralization by 7-17% caused by compost sourced SBO. These findings have relevant implications for the economics and environmental impact of the animal production industry.

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