Simple and rapid separation of Haematococcus pluvialis and ciliate based on the dean-coupled inertial microfluidics.

Astaxanthin with high antioxidant activity is of great practical value and Haematococcus pluvialis is recognized as the best natural astaxanthin producer. The yield of Haematococcus pluvialis was often affected by the ciliate during its production, however, the use of biochemical pesticides might have a great impact on Haematococcus pluvialis. Therefore, a simple microfluidic chip with the spiral microchannel was developed for continuous-flow physical separation of ∼10 µm ciliate from ∼30 µm Haematococcus pluvialis since their different sizes resulted in different equilibrium positions in the channel due to the Dean-coupled inertial migration. First, a spiral microchannel with a width of 700 µm and a height of 130 µm in the microfluidic chip was developed using three-dimensional printing and verified to completely separate polystyrene particles of 10 µm from those of 30 µm. Then, this microfluidic chip was used to separate the actual sample, and experimental results showed that ∼80% of ciliate was continuously separated from Haematococcus pluvialis at a flow rate of 2.8 ml/min. More importantly, no additional biochemical reagents were used and the activity of Haematococcus pluvialis was not affected. This microfluidic chip featured with simple design, automatic operation, and small size is promising for purification and breeding of Haematococcus pluvialis.