In an era where it becomes less and less accepted to just send waste to landfills and release wastewater into the environment without treatment, numerous initiatives are pursued to facilitate chemical production from waste. This includes microbial conversions of waste in digesters, and with this type of approach, a variety of chemicals can be produced. Typical for digestion systems is that the products are present only in (very) dilute amounts. For such productions to be technically and economically interesting to pursue, it is of key importance that effective product recovery strategies are being developed. In this review, we focus on the recovery of biologically produced carboxylic acids, including volatile fatty acids (VFAs), medium-chain carboxylic acids (MCCAs), long-chain dicarboxylic acids (LCDAs) being directly produced by microorganisms, and indirectly produced unsaturated short-chain acids (USCA), as well as polymers. Key recovery techniques for carboxylic acids in solution include liquid-liquid extraction, adsorption, and membrane separations. The route toward USCA is discussed, including their production by thermal treatment of intracellular polyhydroxyalkanoates (PHA) polymers and the downstream separations. Polymers included in this review are extracellular polymeric substances (EPS). Strategies for fractionation of the different fractions of EPS are discussed, aiming at the valorization of both polysaccharides and proteins. It is concluded that several separation strategies have the potential to further develop the wastewater valorization chains.

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In this research, the 80S bioactive glass with different Ca/P ratios was prepared by the sol-gel route. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transforms infrared spectroscopy (FTIR) were used to study the apatite structure and shape. According to the results, the 78SiO2-17P2O5-5CaO bioglass showed a higher rate of crystalline hydroxyapatite (HA) on its surface in comparison with the other bioglasses. After 3 days of immersion in the SBF solution, spherical apatite was formed on the 78SiO2-17P2O5-5CaO surface, which demonstrated high bioactivity. A statistically significant promotion in proliferation and differentiation of G292 osteoblastic cells was also observed. Regarding its optimal cell viability and bioactivity, the 78SiO2-17P2O5-5CaO bioactive glass could be offered as a promising candidate for bone tissue applications.

Crotonic acid (CA) and trans-2-pentenoic acid (2-PA) can be obtained from renewable resources by pyrolysis of the bio-based poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) copolymer. In this study, direct pyrolysis of the PHBV-enriched biomass into CA and 2-PA was studied under an inert atmosphere and N2 carrier gas flow, aiming at obtaining high acid yields from mixed microbial cultures (MMCs). The highest yields of 80 ± 2% for CA and 67 ± 1% for 2-PA were obtained at conditions of 240 °C, 1 h, and 0.15 L/min nitrogen flow rate, corresponding to a mean hot vapor residence time of 20 s. A similar acid yield was achieved when the pyrolysis was performed under reduced pressure (150 mbar) instead of using nitrogen gas. The combined pyrolysis of extracted PHBV at 220 °C and 90 min with vapor fractionation by distillation resulted in yields of 81 and 92% for CA and 2-PA, respectively.

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