Solvent extraction

In the solvent-extraction of .beta.-carotene from an aqueous algal biomass suspension whereby an organic phase in the form of a vegetable oil which is immiscible with water is mixed with a suspension in an aqueous phase of an algal biomass, the biomass containing the .beta.-carotene, to form a mixture of the organic phase and the aqueous phase, whereby the .beta.-carotene is caused to dissolve in the organic phase, followed by separation of the organic phase from the aqueous phase, the method whereby the separation is effected by passing the organic phase containing the dissolved .beta.-carotene through a semi-permeable membrane to effect microfiltration or ultrafiltration of the organic phase, the membrane being of a material which is hydrophobic and the organic phase being passed through the membrane with a pressure drop across the membrane which is lower than that which causes the aqueous phase to pass through the membrane.