Growth of Streptococcus Starter Cultures in Milk Fortified with Nucleic Acid Derivatives

Abstract

Summary Fortification of milk with purines or purine ribosides stimulated acid production by lactic streptococcus starter cultures. Addition of inosine or adenosine resulted in production of more acid than any other individual purine or purine riboside tested. Fortification of milk with pyrimidines is not necessary for the optimum growth of these bacteria. The purine or purine ribosides were interchangeable in the nutrition of these bacteria; they produced as much acid in the presence of inosine as in a mixture of all four naturally occurring purines or purine ribosides. However, growth was slow when none of the exogenous purines or purine ribosides was supplied. Promotion of growth by inosine was not the maximum, because supplementation with pancreas extract resulted in enhanced growth of the cultures.