Microbiological determination of methionine in proteins and foodstuffs.

Kuiken and coworkers (1) reported that methionine is not essential for the growth of Lactobacillue arabinosus 17-5. Later, Hegsted (2), working with the same organism, found that growth failed when methionine was not present in the medium. He called att,ention to the apparent discrepancy in the results obtained in the two laboratories and stated that it was probably due to the use of different strains of the organism. Hutchings and Peterson (3) obtained good growth of Lactobacillus casei without methionine, but found that it was essential for maximum growth. Shankman, Dunn, and Rubin (4) recommend Lo&bacillus casei as most satisfactory for the determination of arginine, glutamic acid, leucine, phenylalanine, tryptophane, tyrosine, and valine, but they do not include methionine. Recently, Dunn and coworkers (5) found that methionine can be assayed with Leuconostoc mesenteroides P-60. Stokes et al. (6) employed Strepto: coccus faecalis for the determination of methionine in several proteins and foods.