Optimization of Fermentation Conditions of the Engineered Corynebacterium Glutamicum to Enhance L-Ornithine Production by Response Surface Methodology

Abstract

Optimization of fermentation conditions for L-ornithine production using the engineered Corynebacterium glutamicum ATCC13032 (? argF? pro? kgd) was carried out by one-factor-at-a-time, Plackett-Burman, the steepest ascent design and a response surface methodology. Addition of Tween 80, tricarboxylic acid cycle intermediates (KAc and succinic acid) improved L-ornithine production. Using Plackett-Burman design, glucose, (NH4)2SO4, MgSO4- 7H2O and yeast extract were screened as significant factors. Response surface methodology was used to further optimize the fermentation medium. The optimized medium contained (g/L): glucose 80.00, yeast extract 13.99, (NH4)2SO4 37.94, MgSO4-7H2O 1.58, KH2PO4 1.00, K2HPO4 0.50, Na2HPO4 0.50, FeSO4-7H2O 0.02, MnSO4-4H2O 0.02, molasses 2.00, KAc 5.00, succinic acid 5.00, CaCO3 10 and Tween 80 1ml (addition after 8 h of fermentation). L-ornithine production was increased by 197 % compared to that under unoptimized conditions. 18.17 g/L of L-ornithine production was obtained at 60 h of fermentation in 5 L bioreactor by the engineered Corynebacterium glutamicum, which is the highest level in engineered strain so far.