Plate assay of thiamine. I. Using Kloeckera brevis.

Lactobacillus fermenti strain 36 is the most frequently used microorganism for the assay of thiamine both in the tube method, (Sarett and Cheldelin, 1944; Fitzgerald and Hughes, 1949), and in the plate method, (Bacharach and Cuthbertson, 1948; Jones and Morris, 1949). Other microorganisms have more recently been suggested for the tube assay; Hoff-Jorgensen and Hansen (1955) used the yeast Kloeckera brevis, and Deibel et al. (1958) used Lactobacillus viridescens. Difficulties are often encountered in the tube methods (Analytical Methods Committee, 1954) but the improved medium of MaciasR (1957) overcomes some of these. However, when the level of thiamine in samples is reasonably high, such as in multivitamin preparations, the L. fermenti plate method may be used; this is far less susceptible to variations than the tube assay with the same microorganism. Plate assays also have the advantages of simplicity and high throughput and, when in use as a routine, the large 12 in. x 12 in. plates, as used by Lees and Tootill (1955) and Simpson and Lees (1956), give assay values with a standard error of + 10 per cent. The present paper describes a plate assay with Kloeckera brevis adapted from the tube method of Hoff-Jorgensen and Hansen. This plate assay has been in use in these laboratories for the past year in parallel with the L. fermenti plate assay.