Effects of dissolved oxygen tension on the production of recombinant penicillin acylase in Escherichia coli

The effect of dissolved oxygen tension (DOT) on over-expression of penicillin acylase (PA) by a recombinant Escherichia coli was studied. Relevant kinetic and stoichiometric parameters were evaluated in batch cultures performed in 1-l bioreactors maintained at constant DOT values in the range of 0–40%. Specific growth rate, biomass concentration, and biomass yield from glucose increased in a Monod-type fashion, whereas acetate and formate concentration decreased as DOT increased. As DOT decreased, specific PA activity at glucose depletion increased from 0.09 to 0.16 U mg−1 dry cell weight (DCW), whereas volumetric PA activity decreased in a Monod-type behavior from 0.25 to 0 U ml−1. The PA activity increased 1.5–3.3-fold when prolonging the culture for 10–25 h after growth cessation. Maximum PA activity was obtained at 1% DOT. Kinetics of PA activity followed a combined growth-associated and non-growth-associated behavior. It is proposed that the Luedeking–Piret coefficients can be expressed as a function of DOT. The growth-associated production coefficient increased with DOT following a Monod-type behavior, whereas the non-growth-associated production coefficient showed a maximum between 1 and 5% of DOT. Moreover, the non-growth-associated coefficient was importantly affected by DOT. Novel control and optimization strategies for DOT can be proposed based in the determined Luedeking–Piret coefficients.