Leibniz Universität Hannover, Institute of Sanitary Engineering and Waste Management, Welfengarten 1, 30167 Hannover, Germany.
J Biotechnol. 2021 Dec 10;342:92-101. doi: 10.1016/j.jbiotec.2021.10.006. Epub 2021 Oct 21.
The production of polyhydroxyalkanoates (PHAs) from waste cooking oil (WCO) by a mixed culture was investigated in the present study at increasing WCO concentrations, temperature and ammonium availability. The PHA production was done in two steps: in the first step, a mixed culture was enriched in PHA-accumulating bacteria from activated sludge in a sequencing batch reactor operated in a feast-famine mode and in the second step the PHA accumulation by the enriched mixed culture was assessed in a batch reactor. In the enrichment step, two substrates, WCO and nonanoic acid were used for enrichment and in the PHA accumulation step only WCO was used. It was not possible to enrich a mixed culture in PHA-accumulating bacteria using WCO as substrate due to the development of filamentous bacteria causing foam formation and bulking in the reactor. However, our results showed that the mixed culture continuously fed with nonanoic acid was enriched in PHA-accumulating bacteria. This enriched culture accumulated both scl- and mcl-PHA using WCO as substrate. The maximum PHA accumulation capacity of this mixed culture from WCO was 38.2% cdw. Increasing the temperature (30-40 ℃) or WCO concentrations (5-20 g/l) increased the PHA accumulation capacity of the mixed culture and the ratios of scl-PHA to mcl-PHA. The presence of ammonium increased PHA accumulation (21.9% cdw) compared to the complete absence of ammonium (5.8% cdw). The thermal characterization of the PHA exhibited the advantageous properties of both scl- and mcl-PHA, i.e., higher melting temperature (152-172 ℃) similar to scl-PHA and a lower degree of crystallinity (12%) similar to mcl-PHA. This is the first study to report the potential of open mixed culture to produce scl- and mcl-PHA from WCO and thus contributing to the understanding of sustainable polymer production.
本研究考察了在不断增加的废烹饪油（WCO）浓度、温度和氨供应条件下，利用混合培养物从 WCO 生产聚羟基烷酸酯（PHA）。PHA 生产分两步进行：第一步，在序批式反应器中采用饥饿-饱食模式，从活性污泥中富集具有 PHA 积累能力的混合培养物；第二步，在批式反应器中评估富集的混合培养物的 PHA 积累能力。在富集阶段，使用 WCO 和壬酸作为两种底物进行富集，而在 PHA 积累阶段仅使用 WCO。由于丝状菌的发展导致反应器中泡沫形成和膨胀，无法使用 WCO 作为底物来富集具有 PHA 积累能力的混合培养物。然而，我们的结果表明，连续用壬酸进料的混合培养物能够富集具有 PHA 积累能力的细菌。这种富集培养物使用 WCO 作为底物积累 scl-和 mcl-PHA。该混合培养物从 WCO 获得的最大 PHA 积累能力为 38.2% cdw。提高温度（30-40℃）或 WCO 浓度（5-20 g/l）均可提高混合培养物的 PHA 积累能力以及 scl-PHA 与 mcl-PHA 的比例。与完全不存在铵（5.8% cdw）相比，铵的存在增加了 PHA 积累（21.9% cdw）。PHA 的热特性表现出 scl-PHA 和 mcl-PHA 的优势特性，即较高的熔融温度（152-172℃）类似于 scl-PHA 和较低的结晶度（12%）类似于 mcl-PHA。这是第一项报道利用开放混合培养物从 WCO 生产 scl-和 mcl-PHA 的潜力的研究，从而有助于理解可持续聚合物生产。
