Microbiological Assay of Amino-Acids with Leuconostoc mesenteroides P.60

Abstract

DUNN et al.^1,2,3 have described four different media, varying in their amino-acid contents, for the microbiological assay of amino-acids by means of the lactic organism Leuconostoc mesenteroides P.60, and consider that one of these media (medium D) is suitable for the assay of lysine and histidine. A re-investigation of medium D has shown that in our hands it is inadequate and acid production is poor. Apparently this has also been found by Dunn et al., for in their third communication³ they recommend the use of 0.05N sodium hydroxide solution instead of 0.1 N. In a fourth paper, Dunn et al.⁴ describe the assay of phenylalanine with a further modification of the medium, in which a still weaker standard solution (0.028 N) is used for titrating the acid produced, although in the assays the contents of six tubes were combined and titrated with 0.111 N sodium hydroxide.