Cao Weifeng, Wang Yujue, Luo Jianquan, Yin Junxiang, Wan Yinhua
State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing P. R. China.
University of the Chinese Academy of Sciences Chinese Academy of Sciences Beijing P. R. China.
Eng Life Sci. 2017 Dec 27;18(3):196-203. doi: 10.1002/elsc.201700142. eCollection 2018 Mar.
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).
α,ω-十二烷二酸（DC）通常用作聚酰胺或某些特殊尼龙的单体。在生物合成过程中，疏水性正十二烷转化为DC时会发生级联氧化，而正十二烷的氧化发生在细胞内空间。因此，研究氧气供应对细胞生长和DC生物合成的作用很重要。研究发现，搅拌速度和通气会影响溶解氧（DO）浓度，进而影响细胞生长以及DC生物合成。然而，培养氧化还原电位（Orp）水平对DC生物合成的影响比DO水平更为显著。对于DC生物合成，第一步是通过正十二烷与细胞的相互作用形成乳液滴。当搅拌速度提高时，乳液滴表面层的缝隙会增加。因此，水通过缝隙的物质运输会增强，从而导致DC产量提高。与在较低搅拌速度（400转/分钟）且无培养氧化还原电位（Orp）控制的分批培养相比，在较高搅拌速度（800转/分钟）下将Orp控制在0 mV以上时，DC浓度提高了5倍，达到201.3 g/L。
