High-level production of arachidonic acid by fed-batch culture of Mortierella alpina using NH4OH as a nitrogen source and pH control.

Mortierella alpina was grown in a fed-batch culture using a 12-l jar fermenter with an initial 8-l working volume containing 20 g glucose l-1 and 10 g corn-steep powder l-1. Glucose was intermittently fed to give 32 g l-1 at each time. The pH of culture was maintained using 14% (v/v) NH4OH, which also acted as a nitrogen source. A final cell density of 72.5 g l-1 was reached after 12.5 days with a content of arachidonic acid (ARA) at 18.8 g l-1. These values were 4 and 1.8 times higher than the respective values in batch culture. Our results suggest that the combined feeding of glucose and NH4+ to the growth of M. alpina could be applied for the industrial scale production of ARA.