Almeida J R, Serrano E, Fernandez M, Fradinho J C, Oehmen A, Reis M A M
UCIBIO-REQUIMTE, Department of Chemistry, Faculty of Sciences and Technology, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
FCC Servicios Ciudadanos, Av. del Camino de Santiago, 40, edificio 3, 4ª planta, 28050 Madrid, Spain.
Water Res. 2021 Jun 1;197:117101. doi: 10.1016/j.watres.2021.117101. Epub 2021 Apr 1.
Phototrophic mixed cultures (PMC) have been found to be a promising technology to produce polyhydroxyalkanoates (PHA), however, work performed thus far has focussed mainly on the use of synthetic feedstocks and operational conditions that differ from those expectable in full-scale processes. The goals of this work were to study, for the first time, the capability of PMCs to produce PHA using real fermented domestic wastewater as feedstock under mixing/light/temperature conditions that are naturally found in outdoor open systems. Various operational strategies were evaluated in this study to increase PHA productivity, namely the poly(3-hydroxybutyric-co-3-hydroxyvaleric) copolymer (PHBV) by PMC systems. Two lab-scale photobioreactors were operated in parallel, with transient illumination (12 h light/12 h dark) and subjected to feedstock fluctuations under two culture selection strategies that best suit the oxidative conditions of high rate algal ponds (HRAPs) which are commonly applied in wastewater treatment plants (WWTP). Under a permanent carbon feast regime (selection strategy 1), the PMC became highly enriched in phototrophic purple bacteria (PPB), and two complementary conditions that can improve the selection of PHA accumulating bacteria were discovered: phosphate cycling, where 20% PHA/VSS (86HB:14HV in a C-mol basis) with a light phase productivity of 0.23 g PHA/L•d_light phase was attained; and transitioning from selection under low organic loading rate (OLR) to high OLR where 17.6% PHA/VSS (60HB:40HV in C base) with a light phase productivity of 0.18 g PHA/L•d_light phase was achieved. Under a feast and famine regime (selection strategy 2), a PMC consortium of microalgae and PPB was obtained, and a multiple pulse feeding strategy during the first hours of the light phase in the selector reactor led to a 26.1% PHA/VSS (36HB:64HV in C base) content, with a productivity of 0.26 g PHA/L•d_light phase and 0.52 g PHA/L•d_feast phase. An accumulation test under higher light intensity led to 30.8% PHA/VSS (85HB:15HV on a C-mol basis) with a productivity of 2.67 g PHA/L•d, along the 8 h of accumulation.
光合混合培养物（PMC）已被证明是一种生产聚羟基脂肪酸酯（PHA）的有前景的技术，然而，迄今为止所开展的工作主要集中在使用合成原料以及与全规模工艺中预期条件不同的操作条件上。本研究的目标是首次研究在室外开放系统中自然存在的混合/光照/温度条件下，光合混合培养物利用实际发酵生活污水作为原料生产PHA的能力。本研究评估了各种操作策略以提高PHA的生产率，即光合混合培养系统生产聚（3-羟基丁酸-co-3-羟基戊酸）共聚物（PHBV）的能力。两个实验室规模的光生物反应器并行运行，采用瞬时光照（12小时光照/12小时黑暗），并在两种最适合污水处理厂（WWTP）中常用的高速率藻塘（HRAP）氧化条件的培养选择策略下承受原料波动。在永久碳盛宴模式（选择策略1）下，光合混合培养物中光养紫色细菌（PPB）高度富集，并且发现了两种可以改善PHA积累细菌选择的互补条件：磷酸盐循环，在此条件下获得了20%PHA/VSS（以碳摩尔计为86HB:14HV），光相生产率为0.23 g PHA/L•d_光相；以及从低有机负荷率（OLR）选择过渡到高OLR，在此条件下实现了17.6%PHA/VSS（以碳计为60HB:40HV），光相生产率为0.18 g PHA/L•d_光相。在盛宴和饥荒模式（选择策略2）下，获得了微藻和光养紫色细菌的光合混合培养物聚生体，并且在选择器反应器中光照阶段的最初几个小时采用多脉冲进料策略导致PHA/VSS含量为26.1%（以碳计为36HB:64HV），光相生产率为0.26 g PHA/L•d_光相，盛宴阶段生产率为0.52 g PHA/L•d_盛宴阶段。在更高光照强度下的积累测试导致在8小时积累过程中PHA/VSS含量达到30.8%（以碳摩尔计为85HB:15HV），生产率为2.67 g PHA/L•d。
