微拟球藻高pH沉降采收的响应面法优化及其培养基的循环利用

Response surface optimization of flocculating Nannochloropsis sp.by pH increasing and reusing of flocculated medium

针对微藻采收成本高的难题,以一株微拟球藻(Nannochloropsis sp.)为研究材料,采用响应面法优化该藻株的高p H沉降采收技术,并初步评估其培养基的循环利用。结果显示,藻株培养液的细胞密度、沉降p H及处理时间3种因素对其生物量采收率(BRR)具有显著影响。预测最优采收参数为:藻细胞光密度OD750=2.08;沉降p H=12.20;处理时间12 h,预测BRR为98.97%,验证实验实测BRR为98.31%。采收藻细胞后的上清液经过滤、p H调整及营养盐补充后,探究高p H采收后的培养基上清液的循环利用。与新鲜培养基相比,高p H采收回收培养基中的藻细胞生长和油脂含量有小幅度的降低,但总脂分级特性及脂肪酸组成无显著差异。该藻株的高p H采收及其培养基的回收利用方法具有可行性。

High-cost harvesting technology is a limitation for industrial cultivation of microglgae. This report deals with the optimization of the high-pH-induced flocculation of a strain of Nannochloropsis sp. using the response surface methodology （RSM）, with which a three-variable, three-level experiment Box-Behnken design （BBD） was developed to examine the effect of initial microalgal cell density （ OD750 ）, pH value and treating time on harvesting efficiency （biomass recovery rate, BRR） of the strain. The results showed that all the three factors significantly influenced the BRR, and the optimum flocculation parameters were as follows： OD750：2.08, flocculating pH：12.20, and treatment time：12 h. Under the optimal condition, the value of BRR attained 98.31%, agreed well with the predicted value （98.97%）. The feasibility of reusing the culture medium after high PH harvesting was further studied after the harvested supernatant treated with pH neutralization and nutrients supplementation. The results indicated that compared with the fresh medium, the medium made with high-pH harvesting supernatant resulted in a slight decrease in growth yield and lipid content, and no obvious changes in lipid distribution and fatty acid profiles, illustrating that reuse of culture medium after high pH-harvesting was acceptable for Nannochloropsis sp. production