Sequential precipitation with different ethanol concentration was also applied for the fractionation of the three peptones. The fractionation was conducted as described by Shen et al. [3] ; 5 fractions were obtained for Hypep 4605 whereas for Hypep 4601 and Hypep 1510, 4 fractions were obtained for each. The effects of the isolated fractions on Vero cells growth were investigated in 24-well plates using a full factorial experimental design; 83 combinations were assessed in duplicate. Two combinations of fractions that show a cell growth comparable to that obtained in IPT-AF medium (positive control), were selected (combinations 1 and 2). The identified combinations were also tested in 6-well plates on 2 g/l Cytodex 1 microcarriers. The highest cell density level reached under these conditions was similar to that achieved in IPT-AF medium.