The necessary CO2 is produced by the organism, but was stripped from the medium by increased aeration rates which led to lower product yields.
Second, medium formulation and aeration rate were optimized, and E. coli BL15 could efficiently convert the renewable substrate glucose to acetoin, one precursor of TMP, with 68.4 g/L by fed-batch fermentation, the record of acetoin production using E. coli.
Table 1 summarizes the cellular fatty acid contents of P. purpureum cultivated under various light intensities and aeration rates in ASW medium.
Fig. 4 Total fatty acid content and fatty acid yield accumulated in P. purpureum under different aeration rates in ASW medium.
Fig. 2 P. purpureum growth under different aeration rates in ASW medium [0.5 L/min (filled square), 1 L/min (filled circle), 1.5 L/min (filled triangle), 2 L/min (filled diamond), and 3 L/min (filled star); cultivation conditions: 25 °C, 110 μmol/m2s, pH 7.6] Fig. 3 Microscopic view of different P. purpureum cells (×400).
To determine if the N. oleoabundans cells are sensitive to the stirring and/or aeration rates, a preliminary set of experiments were performed using 1 L of air/L of medium/min and three different stirring speeds: 150, 300 and 600 rpm.
The rate and yield of the biotransformation were improved by (i) increasing the cell concentration, (ii) using a specially designed vessel with high aeration rates, and (iii) adding an adsorbent resin directly to the biotransformation medium.
Consequently, high agitation rates enable lower aeration rates.
For the process development different aeration rates were tested.
Then, scenarios with a nonuniform distribution of local aeration rates are investigated.
