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In the current study, a mixed microbial culture (MMC) of polyhydroxyalkanoates (PHAs) producers was developed under nutrient stress and was assessed as biocatalyst for the production of high-yielding PHAs from fermented (acidified) discarded fruit juices (DFJ). The structure of the MMC was analyzed periodically to determine its microbial dynamics, revealing that Zoogloae sp. dominated throughout the operation of the system. The efficiency of PHAs production from the MMC was further optimized in batch mode by altering the ratio of C to N, the ratio of carbon sources (propionate and butyrate), and the initial pH, and subsequently different fermentation mixtures of acidified DFJ were assessed as substrates at optimal conditions. Upon solvent extraction, the properties of recovered PHAs were analyzed, showing that in all cases P(3HB-co-3HV) was produced, with T m ranging from 90.5 to 168.8 °C, and maximum obtained yields 54.61 ± 4.31 % and 43.27 ± 2.13 %, from synthetic substrates and DFJ, respectively. Overall, it was shown that the developed MMC can be efficiently applied as biocatalyst for the exploitation of sugary wastewaters, such as DFJ, towards bio-based and biodegradable plastics bearing the required properties to substitute fossil plastics, into the concept of a circular economy., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Gerasimos Lyberatos reports financial support was provided by General Secretariat for Research and Technology. Gerasimos Lyberatos reports a relationship with General Secretariat for Research and Technology that includes: funding grants., (Copyright © 2022 Elsevier B.V. All rights reserved.)