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. 2015 Mar 12;81(7):2256–2264. doi: 10.1128/AEM.03572-14

FIG 6.

FIG 6

Fed-batch culture kinetics of propionic acid production from glycerol with wild-type Propionibacterium jensenii ATCC 4868 and transformants with single and combinatorial expression of the gldA, mdh, and fumC genes. (A) P. jensenii ATCC 4868; (B) P. jensenii(pZGX04-fumC); (C) P. jensenii(pZGX04-mdh); (D) P. jensenii(pZGX04-mdh-fumC); (E) P. jensenii(pZGX04-gldA-fumC); (F) P. jensenii(pZGX04-gldA-mdh). The culture temperature and agitation speed were maintained at 32°C and 200 rpm, respectively. A two-stage pH control strategy was carried out via the automatic addition of Ca(OH)2 (10% [wt/vol]) as follows: the pH was controlled at 5.9 for 0 to 36 h and was shifted to 6.5 after 36 h. Concentrated glycerol (300 g/liter) was fed at a constant rate of 3.33 ml/h between 60 and 132 h of the culture process. Samples were taken from the fermentor every 12 h. △, PA; □, residual glycerol; ■, DCW; ◆, AA; ▲, LA.