Novel integration strategy coupling codon and fermentation optimization for efficiently enhancing sarcosine oxidase (SOX) production in recombinant Escherichia coli.

Sarcosine oxidase (SOX) was an important diagnostic enzyme in the renal function examination. An integrated strategy coupling codon and fermentation optimization was firstly proposed for improving SOX production from recombinant E. coli in 3-L fermentor. The expression suppression (gene phase) and poor balance between SOX expression and cell growth (fermentation phase) in the traditional SOX production were respectively improved by the multiple strategies. Based on the codon bias, the expression suppression was weakened via codon optimization and SOX activity reached 1,521 U/L. The induction toxicity was reduced with the optimal induction condition and SOX production increased to 4,015 U/L. Based on the kinetic analysis of μ x and μ p , a better balance between cell growth and expression was achieved by the two-stage pH-stat control strategy. The SOX activity was further improved to 8,490 U/L and fermentation cycle was also significantly shortened from 44 to 32 h. The substrate inhibition was weakened with a constant feeding fed-batch. With the assistance of integrated strategy, the activity and productivity reached 12,466 U/L and 389.6 U/(L h), respectively, or 3.1-fold and 4.3-fold of the uncontrolled fermentation. The strategy would be also useful in the industrial application of other similar enzymes.