pH诱导絮凝-气浮收获雨生红球藻研究

为提高雨生红球藻(Haematococcus pluvialis)收获效率,文章发现一种通过pH调控诱导雨生红球藻絮凝-气浮收获方法。通过与自然沉降对比发现,在不添加混凝药剂的情况下,调节藻液的pH可以诱导雨生红球藻细胞自发团聚形成絮体,显著提高其沉降或气浮收获效率。pH小于3或大于11.5时,气浮可在2min内实现95%左右的收获效率,而自然沉降则需要30min,才能达到80%—90%的收获效率。气浮收获后的生物质含固率要显著高于沉降收获,当初始浓度为3.2 g/L时, pH诱导絮凝-气浮收获后的雨生红球藻生物质含固率可达到17%,实现了53倍浓缩。另外,与化学混凝剂(硫酸铝)和生物混凝剂(壳聚糖)混凝-气浮对比发现, pH诱导絮凝-气浮不仅可以实现传统药剂混凝-气浮的高收获效率,还可以有效避免混凝剂对生物质的污染(如金属离子残留等),且不会对雨生红球藻中虾青素提取产生影响。因此, pH调控诱导絮凝-气浮可以实现雨生红球藻的快速、高效和无污染收获,为雨生红球藻的收获提供新的解决方案。

HARVESTING HAEMATOCOCCUS PLUVIALIS USING PH-INDUCED DISSOLVED AIR FLOTATION (DAF)

As an important raw material for the extraction of natural astaxanthin, Haematococcus pluvialis is usually harvested by natural sedimentation or centrifugation. However, these harvesting methods either take a long time or consume a lot of energy. This study proposed an efficient method for the harvesting H. pluvialis using pH-induced induced dissolved air flotation (DAF). Harvesting efficiency and solid content, as well as their kinetic curves, were adopted to investigate the influence of pH on the pH-induced DAF harvesting. In addition, the harvesting performances of pH-induced DAF was compared with those of pH-induced sedimentation, chemical coagulant (aluminum sulfate)- and biological coagulant (chitosan)-induced DAF, based on the efficiency and residual metal contents in the harvested biomass. Whether pH treatment affects the astaxanthin content in the harvested biomass was also evaluated, comparing with the content in centrifugation harvested biomass. The results showed that auto-flocculation occurred when the pH of the media was decreased or increased, facilitating the flotation harvesting and sedimentation harvesting of H. pluvialis. pH-induced DAF obtained higher harvesting efficiency and required less separation time, comparing with pH-induced sedimentation. When pH was adjusted to less than 3 or greater than 11.5, the harvesting efficiency of 95% was achieved in 2min using pH-induced DAF, while that took 30min for pH-induced sedimentation to achieve 80%—90% harvesting efficiency. When the initial concentration was 3.2 g/L, the solid content of biomass harvested by pH-induced DAF can reach 17%, realizing 53 times concentration, which was much higher than those harvested by pH-induced sedimentation. Most importantly, pH-induced DAF performed as well as aluminum sulfate and chitosan coagulants induced DAF, while avoiding the impurity of biomass caused by chemical such as Al3+. The astaxanthin contents in H. pluvialis biomass harvested by pH-induced DAF were not affected by the pH treatment. Therefore, harvesting H. pluvialis by pH-induced DAF proved to be a rapid, efficient and environmental sustainable technique, which shed a light on the process development of mass production of H. pluvialis biomass.