Study on the dissolved oxygen control strategy in large‐scale vitamin B 12 fermentation by Pseudomonas denitrificans

BACKGROUND: There are two different routes for vitamin B 12 biosynthesis, which results in discrepancies and uncertainties of the dissolved oxygen (DO) concentration for vitamin B 12 fermentation. In this paper, the DO control strategy was explored for industrial vitamin B 12 fermentation by Pesudomonas denitrificans in 120000‐L fermenter. RESULTS: A DO‐stat strategy was first successfully scaled up from a 9000 L fermenter to a 120 000 L fermenter. Then a multi‐stage DO control strategy was further established in the 120 000 L fermenter, in which the DO level was shifted from 8–10% (20–48 h) to 2–5% (49–106 h) and below 2% (107–168 h) by gradually reducing the rate of aeration and agitation. As a result, 198.80 mg L −1 of vitamin B 12 was obtained, which was significantly higher than those obtained under the fermentations with one‐stage DO control. CONCLUSIONS: The comparatively low DO level was favorable for vitamin B 12 biosynthesis, but it would have an extremely negative effect on cell growth. Compared with the low DO level maintained at all times of the fermentation process, a multi‐stage DO control strategy could not only increase the biomass but also improve vitamin B 12 biosynthesis. Copyright © 2012 Society of Chemical Industry