Osmotic agents for peritoneal dialysis

Claim 1

A process for preparing low molecular weight peptides having a molecular weight between about 300 to about 2000 daltons which comprises: a) treating a high quality protein in an aqueous solution under hydrolyzing conditions, with at least one hydrolytic enzyme, to produce a peptide-containing solution, at least some of the peptides having a low molecular weight between about 300 to about 2000 daltons and at least some of the peptides having a molecular weight above about 2000 daltons; b) passing the peptide-containing solution into contact with one side of a dialysis membrane while substantially pure water, obtained from step (d) herein is passing in contact with the other side of said dialysis membrane under effective dialysis separation conditions, said dialysis membrane being effective to allow transport therethrough of the low molecular weight peptides having molecular weight between about 300 to about 2000 daltons while retaining the peptides having a molecular weight above about 2000 daltons in the peptide-containing solution and said water having a sufficiently low peptide solute concentration effective to allow transport of the low molecular weight peptides across the membrane into the water; c) passing the water and the transported low molecular weight peptides contained therein from the other side of the dialysis membrane to a reservoir; d) passing water, containing transported low molecular weight peptides, from the reservoir into contact with one side of a reverse osmosis (RO) membrane under reverse osmosis separation conditions, including pressure, effective to cause substantially pure water to be transported across said RO membrane to provide a quantity of substantially pure water for use in step (b) herein and to retain at said one side of said RO membrane a quantity of water containing the transported low molecular weight peptides at a higher concentration than in the water passing to the RO membrane; and e) passing the water containing the transported low molecular weight peptides at a higher concentration from said one side of said RO membrane to the reservoir to provide in the reservoir an aqueous solution of low molecular weight peptides at a concentration substantially higher than in the water containing the transported low molecular weight peptides passing to the reservoir in step (c), herein.