The selection and enrichment of a mixed microbial culture (MMC) for polyhydroxyalkanoates (PHA) production is a well-known technology, typically carried out in sequencing batch reactors (SBR) operated under a feast-famine regime. With a nitrogen-deficient carbon source to be used as feedstock for PHA synthesis, a nutrient supply in the SBR is required for efficient microbial growth. In this study, an uncoupled carbon (C) and nitrogen (N) feeding strategy was adopted by dosing the C-source at the beginning of the feast and the N-source at the beginning of the famine, at a fixed C/N ratio of 33.4 g COD/g N and 12 h cycle length. The applied organic loading rate (OLR) was increased from 4.25 to 8.5 and finally to 12.725 g COD/L d. A more efficient selective pressure was maintained at lower and intermediate OLR, where the feast phase length was shorter (around 20% of the whole cycle length). However, at the higher OLR investigated, the PHA content in the biomass reached a value of 0.53 g PHA/g VSS at the end of the feast phase, as a consequence of the increased C-source loaded per cycle. Moreover, 2nd stage PHA productivity was 2.4 g PHA/L d, 1.5 and 3.0-fold higher than those obtained at lower OLR. The results highlight the possibility of simplifying the process by withdrawing the biomass at the end of the feast phase directly to downstream processing, without a need for the intermediate accumulation step.

中文翻译：

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在非耦合碳和氮进料的序批式反应器中高速选择 PHA 积累混合培养物

用于聚羟基链烷酸酯 (PHA) 生产的混合微生物培养物 (MMC) 的选择和富集是一项众所周知的技术，通常在大饥荒制度下运行的序批式反应器 (SBR) 中进行。将缺氮碳源用作合成 PHA 的原料，SBR 中的营养供应是微生物有效生长所必需的。在这项研究中，采用非耦合的碳 (C) 和氮 (N) 补料策略，在盛宴开始时添加碳源，在饥荒开始时添加氮源，以固定的 C/N 比33.4 g COD/g N 和 12 小时循环长度。应用的有机负载率 (OLR) 从 4.25 增加到 8.5，最终增加到 12.725 g COD/L d。在较低和中等 OLR 下保持更有效的选择压力，其中盛宴阶段的长度较短（大约是整个周期长度的 20%）。然而，在更高的 OLR 研究中，由于每个循环加载的碳源增加，生物质中的 PHA 含量在盛宴期结束时达到 0.53 g PHA/g VSS 的值。此外，第二阶段 PHA 生产率为 2.4 g PHA/L d，比在较低 OLR 下获得的生产率高 1.5 和 3.0 倍。结果突出了通过在盛宴阶段结束时将生物质直接提取到下游加工而无需中间积累步骤来简化过程的可能性。第二阶段 PHA 生产率为 2.4 g PHA/L d，比在较低 OLR 下获得的生产率高 1.5 和 3.0 倍。结果突出了通过在盛宴阶段结束时将生物质直接提取到下游加工而无需中间积累步骤来简化过程的可能性。第二阶段 PHA 生产率为 2.4 g PHA/L d，比在较低 OLR 下获得的生产率高 1.5 和 3.0 倍。结果突出了通过在盛宴阶段结束时将生物质直接提取到下游加工而无需中间积累步骤来简化过程的可能性。