Process for producing vitamin B.sub.12 by the fermentation technique, and vitamin B.sub.12 -producing microorganism

Abstract

A process for producing vitamin B.sub.12 by the fermentation technique which comprises cultivating a vitamin B.sub.12 -producing microorganism belonging to the genus Propionibacterium in a culture medium containing a carbon source and a nitrogen source, and collecting vitamin B.sub.12 accumulated in the cells of the microorganism; characterized in that (1) the cultivation is carried out while adding an alkali at suitable times to the cultivation system so that during the cultivation, the cultivation system is maintained at a pH in the range of about 5 to about 7.5, and (2) the cultivation is carried out while adding a carbon source portionwise to the cultivation system nearly at the same time as the addition of the alkali, (3) provided that when a vitamin B.sub.12 -producing microorganism having resistance to propionic acid is used as the microorganism, the portionwise addition of the carbon source in (2) can be omitted. Also disclosed are propionic acid-resistant, vitamin B.sub.12 -producing microorganism of the genus Propionibacterium.

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