一种富集高温栅藻Desmodesmus sp. F51的新型生物絮凝剂

Effective harvesting of the microalgae Desmodesmus sp. F51 with a novel bioflocculant

[背景]海科贝特氏菌(Cobetia marina)可产生大量具有絮凝活性的胞外产物,可视为一种新型的生物絮凝剂。高温栅藻(Desmodesmus sp.F51)是一种具有较高叶黄素含量的微藻,被认为是一种新兴的叶黄素来源,但利用该生物絮凝剂高效富集高温栅藻的相关研究迄今尚未见报道。[目的]以高温栅藻为对象,研究该新型生物絮凝剂的絮凝效率,并对絮凝机理进行初步探讨。[方法]探索在不同生长阶段微藻培养液添加生物絮凝剂、添加量、絮凝时间、pH对絮凝效率的影响,分析生物絮凝剂的功能基团,并测定在不同pH条件下添加生物絮凝剂前后高温栅藻的Zeta电位变化,以及在显微镜下分析藻细胞在添加生物絮凝剂前后的形态。[结果]在高温栅藻生长至稳定期(pH 8.0)添加2 mL生物絮凝剂,絮凝15 min絮凝效果最佳,达82.1%。傅里叶红外光谱(fourier transform infrared spectroscopy,FTIR)显示了多糖及酰胺结构的特征吸收峰,由此推测生物絮凝剂主要是多糖的混合物,含有少量蛋白质。根据Bradford法测定絮凝剂中蛋白含量约为0.4%(质量比),通过苯酚-硫酸法测定总糖质量分数约为34.5%(质量比),与FTIR分析结果基本相符。生物絮凝剂在pH 4.0-11.0保持60%以上的絮凝效率,说明无论是酸性或是碱性条件下絮凝效率都较高,结合Zeta电位的分析表明,推测生物絮凝剂对高温栅藻的絮凝机理中占主导地位的可能是吸附架桥作用。[结论]该研究对微藻生物絮凝具有重要的理论和实践意义。

[Background] Cobetia marina can produce many extracellular products with flocculation activity and therefore is regarded as a novel bioflocculant. Desmodesmus sp. F51 is one of the best new resources for natural xanthophyll due to its ability to accumulate large amounts of lutein. However, up to date there is no report on the use of bioflocculant from Coberia marina for Desmodesmus sp. F51 harvesting. [Objective] The flocculation efficiency and mechanism of the new biological flocculant on Desmodesmus sp. F51 were investigated. [Methods] Effects of bioflocculant addition in different growth periods, the addition amount of bioflocculant, flocculation time and p H on flocculation efficiency were investigated. The functional groups of bioflocculant were analyzed. Zeta potential of Desmodesmus sp. F51 before and after the addition of bioflocculant under different p H conditions were measured, and the morphology of Desmodesmus sp. F51 under the microscope before and after the addition of bioflocculant were also analyzed. [Results] The highest flocculating efficiency(82.1%, 15 min, pH 8.0) was achieved when 2 m L of bioflocculant was added at the stationary growth phase of Desmodesmus sp. F51. Fourier transform infrared spectroscopy analysis showed the characteristic structure of polysaccharides and amide. Thus, it was speculated that the bioflocculant was mainly a mixture of heteropolysaccharides, containing a small amount of proteins. According to Bradford method, the protein content in the bioflocculant was about 0.4%(W/W) and the total sugar content determined by phenol-sulfuric acid method was about 34.5%(W/W), which was basically consistent with the results of fourier transform infrared spectroscopy analysis. The flocculating efficiency is above 60% when the pH value ranges from 4.0 to 11.0, which indicates that the flocculation efficiency is higher under both acidic and alkaline conditions. The analysis of Zeta potential indicates that the dominant flocculation mechanism of the bioflocculant may be adsorption bridging. [Conclusion] This study is of great significance for microalgae harvesting by bioflocculation.