Characterization of casein peptones by HPLC profiles and microbiological growth parameters

Thirty six pancreatic casein peptones from various producers were analyzed by HPLC and by microbiological growth tests. The data were compared by using the principal coordinate analysis and simple mathematical tests. The Proteose peptone quotient, PQ1, determined by the growth of Escherichia coli, separated these casein peptones into three groups, depending on their suitability as nutrients compared to Proteose peptone as a standard. These groups corresponded to the HPLC patterns, characterized by the specific peaks of polypeptides, peptides and amino acids, respectively. The peaks of the high-molecular weight polypeptides were negatively correlated with the growth parameters. The peptides of a low molecular weight promoted the growth of Staphylococcus aureus with and without the exhaustion of usable N compounds and in the presence and absence of glucose (PQ2 and PQ3). The colony sizes correlated weakly with certain peaks only. HPLC patterns, thus, seem to be useful for the characterization of casein peptones for the standardization of nutrient media as well as for special applications.