抄録
The microbiological tube assay of vitamin B_<12> with a mutant of E. coli produced by Hayashi as a test organism was discussed. Determinations carried out on activated sludge, digested sludge and anaerobic fermentation products from distillers' plants indicate that E. coli mutant method gives results which are comparable to those obtained with L. leichmannii method. The former is also better in much lower expenses for basal medium as well as in good response to vitamin B_<12>.
