抄録
The vitamin B_<12> activities in various fibrous materials were investigated to see if the cotton used for stopper could cause the high blank, occasionally observed in the determination of vitamin B_<12> with Lactobacillus leichmannii. The amount of true vitamin B_<12> in cotton could be supposed to be very small, since the apparent vitamin B_<12> activity obtained was 2.0-2.5mγ/g and alkali stable factor was 1.6mγ/g. No growth promoting effect was observed in acetate-, vinilon-, and viscose-fibre when added to the assay medium in the form of aqueous extracts of those fibres, although vitamin B_<12> activity was recognized when added in solid form.
