Disclosed is an ex-vivo method for producing a processed protein rich stream comprising: separating a blood-free fluid stream derived from a peritoneal cavity into a protein-rich stream and an ultrafiltrate, and processing at least some of the protein-rich stream to produce a processed protein rich stream, which includes the use of a sorbent system having an enzyme that is immobilized on a substrate with greater than Van der Waals forces wherein the sorbent removes at least one toxin from at least some of the protein-rich stream wherein the processed protein rich stream is suitable for introduction into the peritoneal cavity and wherein at least 80% of the substantially blood-free stream is suitable for introduction into the peritoneal cavity as a processed protein rich stream over a period of 8 hours. The method is useful as part of a peritoneal dialysis system.
