Concentration and desalting by membrane processes of a natural pigment produced by the marine diatom Haslea ostrearia Simonsen

Abstract

The marine microalga Haslea ostrearia, also called ≪blue navicula⪢, presents the unique peculiar property among the diatoms, to produce at its extremities a blue hydrosoluble pigment called ≪marennine⪢. It is presented the concentration and the desalting of the exocellular pigment by membrane processes (ultrafiltration, nanofiltration, reverse osmosis). Nanofiltration is particularly developed given the potential of this type of application both for the concentration of molecules and for desalting. It is shown the effect of velocity and pressure on performances of nanofiltration membranes. Permeation flux superior to 100 l h −1 m −2 (at 14.10 5 Pa) are obtained with the Kiryat Weizmann membrane MP 20 (polyester coated with a polyacrylonitrile layer, cut-off 450 Da). For the desalting of the blue pigment solution, nanofiltration membranes present a few advantages: a low salt rejection (less than 10% at 14.10 5 Pa) and a high pigment rejection (the nanofiltration membrane MP 20 retains more than 95% of the pigment). This membrane used in diafiltration mode allows an acceptable speed of desalting (700 g of salt eliminated per hour and per m 2 at 25.10 5 Pa for a concentration of 18 g of salt per litre of solution).