Niacin assay by monitoring changes in electrical conductance caused by microbial growth

A computerized Malthus 128 H Growth Analyser was used to determine the changes in conductance produced by growth of a niacin-dependent strain of Lactobacillus plantarum ATCC 8014 in different concentrations of niacin in the growth medium. Changes in conductance varied linearly with the niacin concentration in the range 5-50 ng/ml. The time required to complete a test is inversely related to the inoculum size, and results can be obtained after 6 h.