Abstract
AbstractBACKGROUNDPrevious research proved that fermentation via dissolved oxygen (DO) step‐wise reduction was favorable for vitamin B12 productivity by Pseudomonas denitrificans, but the high‐production mechanism is still unclear. Based on this fact, P. denitrificans metabolic characteristics under different DO supply models were investigated in a 5 L fermenter by assaying the activities of the key enzymes involved in central carbon metabolism and the vitamin B12 biosynthetic pathway.RESULTSCompared with fermentation processes under the DO‐stat strategy and DO step‐wise increase, it was found that DO step‐wise reduction for P. denitrificans fermentation could significantly strengthen the Embden–Meyerhof–Parnas flux and weaken the tricarboxylic acid cycle and hexose monophosphate pathway, but also facilitate the activities of δ‐aminolevulinic acid synthase and porphobilinogen synthase.CONCLUSIONSWhen P. denitrificans fermentation was implemented using DO step‐wise reduction, the metabolic characteristics indicated that more precursors for vitamin B12 biosynthesis could be generated. As a result, a significant improvement in vitamin B12 productivity was achieved (69.09 ± 4.48 mg L−1). © 2013 Society of Chemical Industry
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