Abstract

An automated method for the microbiological assay of vitamin B₁₂ is described. A chloramphenicol-resistant strain of Lactobacillus leichmannii is used as the test organism and this eliminates the need for sterilization or aseptic addition. Precipitation of the serum protein is avoided by dilution of the serum with a glutamic/malic acid solution before heating the preparation to free the vitamin B₁₂. Tests can be set up at a rate of 80 an hour and after incubation they can be read at 160 an hour. By interfacing a programmed electronic calculator directly with the Mecolab M which is used for the assays, results are printed directly in ng/l.