Supporting data for "Production of Polyhydroxyalkanoates (PHAs) from urban food waste with mixed microbial culture"

As urban areas expand and economies advance, municipal solid waste accumulation becomes a pressing concern world wild. Among various urban wastes, food waste (FW) is a major component. The typical Chinese FW is predominantly starch-based, offering rich resources including carbon, nitrogen, and phosphorus. This makes it an optimal candidate for anaerobic fermentation (AF), wherein the wasted carbon is transformed into volatile fatty acids (VFA) and subsequently used to produce PHA. In light of this, this study delves into an innovative biological process that integrates FW fermentation with a PHA mixed microbial culture (MMC) to accomplish waste reduction and simultaneous resource recovery.

In the combination of FW fermentation and single-stage PHA MMC, a substantial COD_VFA/g VS₀ of 0.51 ± 0.07 g was gained with a COD_VFA/COD of 0.7 during FW fermentation for effective PHA accumulation. Across a 198-day span, overall 80% COD_VFA was removed, and a maximum PHA content rate of 39.1 ± 7.7 g/g VSS with a yield of 0.17 ± 0.06 g/g COD_VFA was achieved. An overall yield of 8.0% wt PHA/COD_VFA was estimated based on the mass balance calculation. Bioinformatics analysis results revealed that Xanthobacter was the most dedicated contributor to PHA producing with an abundance remaining at almost 60% regardless of changes in carbon source, loading rate, or nutrients amount.

Despite FW, the wasted activated sludge (AS) generated by wastewater treatment plants (WWTPs), also constitutes a significant portion of urban waste. The co-fermentation of FW and AS enhanced VFA production, yielding a COD_VFA/g VS₀ of 0.43 ± 0.06 g and a high COD_VFA/COD of 78.5%. Over the 186 days of operation, the PHA MMC achieved a peak PHA% of 40.0 ± 4.2 g/g VSS, with a yield of 0.14 ± 0.07 g/g COD_VFA, and an overall PHA yield of 12.5% wt PHA/ COD_VFA daily. The incorporation of AS for fermentation notably elevated the proportion of propionate in VFAs, leading to a transition from polyhydroxybutyrate (PHB)-dominant to polyhydroxyvalerate (PHV)-dominant PHA composition. The 16S rRNA analysis revealed the genus Mesorhizobium crucially contributed to PHA generation, maintaining dominance throughout the whole operation period.

To address the distinct kinetics for biomass growth and PHA accumulation, and to mitigate the adverse effects of PHA production-related sludge bulking, a novel waste conversion system which comprised of an FW fermenter and a 2-stage PHA MMC was studied. The FW fermentation yielded a COD_VFA/g VS₀ of 0.53 g and a COD_VFA/COD of 73.2%, which served as feedstock for the 2-scale system spanning 120 days. Throughout this period, a PHA accumulation of 46.4% was achieved, with a PHA yield of 0.16, ultimately attaining a maximum daily PHA production yield of 12.1% wt PHA/ COD_VFA. 16S rRNA analysis revealed consistent trends in the functional microbial community of the 2-stage MMC that the initially dominated Leucobacter and Xanthobacter were gradually instead of. the coexistence of diverse functional microorganisms. Overall, the findings of this study suggested the combination of FW-based fermentation and PHA MMC holds promise as an appropriate technology for urban waste reduction and resource recovery.