Construction of a Bioreactor with Immobilized Yeast Cells for Production of a Low-phenylalanine Peptide Mixture as a Phenylketonuria Foodstuff

Abstract

This work aimed at establishing a process for removal of phenylalanine from the enzymatic hydrolysate of a milk whey protein preparation to obtain a low-phenylalanine peptide mixture. Rhodotorula rubra IAM 4989 was screened as the most suitable strain for metabolizing phenyl-alanine with no appreciable product inhibition. The intact cells indiscriminately consumed all the constituents of the enzymatic hydrolysate, but cells entrapped in a polypyrrole matrix consumed only low-molecular-weight components to give a low-phenylalanine peptide mixture in a high yield. This selectivity was due to the different permeabilities of the constituents of the hydrolysate through the polypyrrole membrane. The entrapped cells retained their phenylalanine-decomposing activity for at least 4 weeks.