Abstract
Polyhydroxyalkanoates (PHAs) are a potential substitute for traditional plastics. Synthesis of PHAs using excess sludge without additional domestication as a mixed microbial culture can reduce production costs. PHAs were synthesized using excess sludge (R1) from a continuous flow system performing simultaneous nitrification/denitrification and phosphorus removal. Excess sludge (R2) from a A2O wastewater treatment plant was used as a mixed microflora culture (MMC) and the waste fermentation liquid was used as a carbon source. Results showed that with volatile fatty acid (VFA) concentrations of 430–520 mg/L (COD of 650–750 mg/L), when R1 and R2 were reacted under anaerobic conditions, the maximum generated concentrations of PHAs were 84.41 mg/g and 30.8 mg/g, respectively. When aeration volumes were 5, 10, 15, and 20 L/h, the amounts of PHAs synthesized from R1 and R2 increased by varying degrees, with the highest amount generated at 10 L/h (108.6 mg/g and 58.58 mg/g, respectively). In the process of PHA formation, ORP shows a decreasing trend. When the concentration of PHAs reaches a maximum level, ORP drops to a “valley point.” Lower ORP valley points indicate a higher potential for synthesis of PHAs. Therefore, ORP can be used as a control parameter to reflect the reaction process in the micro-oxygen synthesis of PHAs.
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Acknowledgments
The authors would like to thank Guangzhou University for its support.
Funding
This project was financially supported by the National Natural Science Foundation of China (Grant No. 21207023) and the Natural Science Foundation of Guangdong Province (Grant No. 2017A030313273).
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Highlights
• Undomesticated excess sludge from two sewage treatment processes was used to investigate the capacity for PHA synthesis.
• The yield of synthetic PHAs from undomesticated excess sludge was increased through micro-aeration.
• The presence of DO was conducive to the synthesis of intracellular glycogen by microorganisms.
• ORP can be used as a control parameter in the process of micro-oxygen PHA synthesis.
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Fang, Q., Huang, Z., Liu, Y. et al. Micro-oxygen Process Improved Synthesis of PHAs with Undomesticated Excess Sludge. Appl Biochem Biotechnol 192, 367–380 (2020). https://doi.org/10.1007/s12010-020-03322-w
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DOI: https://doi.org/10.1007/s12010-020-03322-w