Cultivation of a Starch-rich Microalga Desmodesmus insignis in Dairy Wastewater and Removal of Nitrogen and Phosphorus
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摘要: 为了研究标志链带藻(Desmodesmus insignis strain JNU24)在不同NaNO3浓度和不同废水浓度培养下的生长与代谢产物积累状况,评估标志链带藻对废水的处理能力,本研究利用柱状光反应器对标志链带藻进行培养,分别对4种NaNO3浓度的BG-11培养基和4种废水浓度培养下藻细胞的生物量、蛋白质含量、碳水化合物含量和淀粉含量进行了测定。结果显示,在BG-11培养基中,氮浓度为9.0mmol/L时,藻细胞生物质浓度最高,达6.23g/L;在废水培养下,未稀释的原废水实验组,其藻细胞生物质浓度最高,达10.31g/L;75%废水培养下,藻细胞的淀粉含量最高(达50.9%),单位体积藻细胞淀粉含量和产率分别为4.86g/L和405mg·L-1·d-1,且显著高于不同浓度NaNO3的BG-11培养基组。本研究还测定了标志链带藻对废水中氮、磷的去除效率,结果显示不同浓度废水培养下,氮、磷的去除效率最高可达90.8%和98.7%。基于柱状反应器中的最佳培养效果,以9.0mmol/LNaNO3的BG-11培养基和75%废水于3.0cm光径平板光生物反应器中进行室内扩大培养,结果显示在75%废水培养下,藻细胞生物质浓度达9.75g/L,淀粉单位体积含量和产率分别达到4.75g/L和230mg·L-1·d-1,且为9.0mmol/LNaNO3的BG-11培养基培养的3倍。通过沉降特性分析发现,藻细胞收获90min后均完全沉降,具有较强的沉降性能。本研究标志链带藻能够耐受废水中较高的氮、磷浓度,且对废水中氮、磷有显著的去除作用;该藻能利用废水中的营养成分积累较高的生物量和淀粉含量并且藻细胞能快速沉降,具有极高的经济价值和应用价值,是一株淀粉生产能力较高和废水处理能力较强的极具开发潜力的藻株。Abstract: Desmodesmus insignis strain JNU24 was cultivated in BG-11 medium containing four different initial NaNO3 concentrations and dairy wastewater (DWW) diluted into four concentrations to compare its growth, starch production performance, and nitrogen and phosphorus removal capacity in DWW. Results indicated that the optimum nitrate concentrations and DWW concentration for growth were 9.0 mmol/L and 100%, respectively, in which biomass achieved was 6.23 g/L and 10.31 g/L, respectively. Compared with the BG-11 group, however, D. insignis showed a greater ability to grow and accumulate starch when cultivated with 75% DWW, in which the starch content, volumetric starch content, and productivity reached 50.9%, 4.86 g/L, and 405 mg·L-1·d-1 respectively. In addition, D. insignis removed 90.8% of nitrogen and 98.7% of phosphorus from DWW. Indoor scaled-up cultivation of D. insignis was carried out in vertical flat-plate glass photobioreactors based on optimum concentrations of BG-11 and DWW. The maximum biomass concentration, volumetric starch content, and productivity of D. insignis were obtained under 75% DWW, reaching 9.75 g/L, 4.75 g/L, and 230 mg·L-1·d-1, respectively, which were approximately two times greater than those obtained in the BG-11 group. These results showed that D. insignis could tolerant high nitrate concentrations in DWW, and could be applied on a large scale with cheap media. The D. insignis cells exhibited outstanding settling capacity, as inferred from their ability to settle within 90 min in 75% DWW after stopping aeration. In conclusion, D. insignis is a microalga that has the potential to produce starch and purify wastewater.
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Keywords:
- Desmodesmus insignis /
- Wastewater treatment /
- Settling velocity /
- Starch /
- Bioethanol
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