Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China,
Appl Microbiol Biotechnol. 2015 Feb;99(3):1531-41. doi: 10.1007/s00253-014-6288-0. Epub 2014 Dec 18.
Bacterial contamination and biomass harvesting are still challenges associated with coupling of microalgae and wastewater treatment technology. This study investigated aggregation, bacterial growth, lipid production, and pollutant removal during bacteria contaminated Chlorella regularis cultivation under nutrient starvation stress, by supposing the C/N/P ratios of the medium to 14/1.4/1 (MB₂.₅) and 44/1.4/1 (MB₄.₀), respectively. Granules of 500-650 μm were formed in the bacteria contaminated inoculum; however, purified C. regularis were generally suspended freely in the medium, indicating that bacterial presence was a prerequisite for granulation. Extracellular polymeric substance (EPS) analysis showed that polysaccharides were dominant in granules, while protein mainly distributed in the outer layer. Denaturing gradient gel electrophoresis (DGGE) results revealed Sphingobacteriales bacterium and Sphingobacterium sp. are vital organisms involved in the flocculation of microalgae, and nitrifiers (Stenotrophomonas maltophilia) could co-exist in the granular. Both EPS and DGGE results further supported that bacteria played key roles in granulation. C. regularis was always dominant and determined the total biomass concentration during co-cultivation, but bacterial growth was limited owing to nutrient deficiency. Starvation strategy also contributed to enhancement of lipid accumulation, as lipid content in MB₄.₀ with a greater C/N/P led to the greatest increase in the starvation period, and the maximum lipid productivity reached 0.057 g/(L·day). Chemical oxygen demand and nitrogen removal in MB₄.₀ reached 92 and 96%, respectively, after 3 days of cultivation. Thus, cultivation of microalgae in high C/N/P wastewater enabled simultaneous realization of biomass granulation, bacterial overgrowth limitation, enhanced lipid accumulation, and wastewater purification.
细菌污染和生物量收获仍然是与微藻和废水处理技术耦合相关的挑战。本研究通过假设培养基的 C/N/P 比分别为 14/1.4/1（MB₂.₅）和 44/1.4/1（MB₄.₀），研究了在营养饥饿胁迫下受细菌污染的普通小球藻培养过程中的聚集、细菌生长、油脂生产和污染物去除。在受污染的接种物中形成了 500-650μm 的颗粒；然而，纯化的 C. regularis 通常自由悬浮在培养基中，这表明细菌的存在是颗粒形成的前提条件。胞外聚合物（EPS）分析表明，多糖在颗粒中占优势，而蛋白质主要分布在外层。变性梯度凝胶电泳（DGGE）结果表明，鞘脂杆菌和鞘氨醇单胞菌是参与微藻絮凝的重要生物，硝化菌（嗜麦芽窄食单胞菌）也可以在颗粒中共存。EPS 和 DGGE 结果进一步表明，细菌在颗粒形成中起着关键作用。在共培养过程中，C. regularis 始终占优势并决定总生物量浓度，但由于营养缺乏，细菌生长受到限制。饥饿策略也有助于增强油脂积累，因为在 MB₄.₀ 中较大的 C/N/P 导致饥饿期的最大增加，最大油脂生产力达到 0.057 g/（L·天）。在培养 3 天后，MB₄.₀ 中的化学需氧量和氮去除率分别达到 92%和 96%。因此，在高 C/N/P 废水中培养微藻可以同时实现生物量颗粒化、细菌过度生长限制、增强油脂积累和废水净化。
