Selective removal of hydrophobic peptides from protein hydrolysates in a continuous supported liquid membrane process

The removal of hydrophobic peptides from a casein hydrolysate solution through a supported liquid membrane (SLM) was investigated in a continuous flow system. The liquid membrane was formulated with an anionic surfactant (Aerosol OT) as the carrier and oleyl alcohol as the organic phase on a Celgard 2500 as support. A mixture of amino acid (tryptophan) and dipeptide (tryptophanleucine) was examined to determine the pH at which the transport of peptide is preferentially faster than that of the amino acid. At this feed pH the effects of the following variables were examined: hydrolysate concentration, feed and strip phase flow rate, and carrier concentration in membrane preparation. The stability of SLM for long-term continuous operation was studied, and the regeneration of SLM was tried for repeated use. It was demonstrated that the following conditions are favourable for the selective removal of peptides: 1) a feed solution pH of 4.5, 2) a dilute feed concentration (<20 g/L), 3) slower feed and strip flow rates (<20 mL/h), 4) a liquid membrane prepared with 10-20% carrier, and 5) a regeneration scheme after every 24 hours.