Protoplast preparation from enriched flagellates and resting cells of Haematococcus pluvialis.

AIMS: To establish a proper protoplast-preparation route from enriched motile flagellates and nonmotile resting cells of Haematococcus pluvialis.

METHODS AND RESULTS: Through cultivations in two mixotrophic media, enriched Haematococcus flagellates and resting cells were respectively produced and applied in enzymatic protoplast preparations. Great differences of enzymatic sensitivity and osmotic-lability were identified between them. Flagellates showed the same osmotic-lability as protoplasts and the extracellular matrix-removing rate was applied for an evaluation of protoplast-releasing. During the treatment of flagellates, an addition of more than 0·2 mmol l-1 Ca2+ was found to be essential for maintenance of high cellular viability. More than 80% cellular viability and a 90% protoplast-releasing rate were obtained simultaneously after 2-3 h treatment of 0·06% proteinase K in 0·05 mol l-1 Tris-HCl (pH7·8) buffer with 0·2 mmol l-1 CaCl2 and 0·2 mol l-1 sorbitol/mannitol. For resting cells, a treatment of both 0·12% proteinase K and a combination of 2% cellulase + 1% snailase could function similarly in order to degrade the cellulosic cell wall, while the protoplast yield was limited to about 40%, due to the existence of an undegradable secondary wall in the mature resting cell.

CONCLUSION: Proteinase K was efficient for protoplast-releasing from either flagellates or resting cells. Due to the great difference of enzymatic sensitivity and osmotic-lability between flagellates and resting cells, it was necessary to select a different enzymatic treating process based upon the main cell type in the culture. A better protoplast-preparing efficiency was obtained from Haematococcus cells when flagellates were in the majority.

SIGNIFICANCE AND IMPACT OF THE STUDY: The protoplast preparation of H. pluvialis was firstly established based on two main cell types of H. pluvialis, motile flagellates and nonmotile resting cells. Increase of flagellate stability and viable protoplast-preparing efficiency through addition of Ca2+ in enzymatic solution was firstly reported.