Role of oxygen supply in α, ω-dodecanedioic acid biosynthesis from n-dodecane by ipe-1: Effect of stirring speed and aeration.

α, ω-Dodecanedioic acid (DC) usually serves as a monomer of polyamides or some special nylons. During the biosynthesis, oxygenation cascaded in conversion of hydrophobic n-dodecane to DC, while the oxidation of n-dodecane took place in the intracellular space. Therefore, it was important to investigate the role of oxygen supply on the cell growth and DC biosynthesis. It was found that stirring speed and aeration influenced the dissolved oxygen (DO) concentration which in turn affected cell growth as well as DC biosynthesis. However, the effect of culture redox potential (Orp) level on DC biosynthesis was more significant than that of DO level. For DC biosynthesis, the first step was to form the emulsion droplets through the interaction of n-dodecane and the cell. When the stirring speed was enhanced, slits in the surface layer of the emulsion droplets would be increased. Thus, the substances transportation by water through the slits would be intensified, leading to an enhanced DC production. Compared with the batch culture at a lower stirring speed (400 rpm) without culture redox potential (Orp) control, the DC concentration was increased by 5 times up to 201.3 g/L with Orp controlled above 0 mV at a higher stirring speed (800 rpm).