Kim, Dong-Hoon5; Lee, Ji-Hye5; Hwang, Yuhoon1; Kang, Seoktae6; Kim, Mi-Sun4
1 Department of Environmental Engineering, Technical University of Denmark2 Korea Institute of Energy Research3 Kyung Hee University4 Korea University of Science and Technology5 Korea Institute of Energy Research6 Kyung Hee University
In the present work, we introduced a novel approach for microbial fatty acids (FA) production. Photosynthetic bacteria, Rhodobacter sphaeroides KD131, were cultivated in a continuous-flow, stirred-tank reactor (CFSTR) at various substrate (lactate) concentrations.At hydraulic retention time (HRT) 4 d, cell concentration continuously increased from 0.97 g dcw/L to 2.05 g dcw/L as lactate concentration increased from 30 mM to 60 mM. At 70 mM, however, cell concentration fluctuated with incomplete substrate degradation. By installing a membrane unit to CFSTR, a stable performance was observed under much higher substrate loading (lactate 100 mM and HRT 1.5 d). A maximum cell concentration of 16.2 g dcw/L, cell productivity of 1.9 g dcw/L/d, and FA productivity of 665 mg FA/L/d were attained, and these values were comparable with those achieved using microalgae. The FA content of R. sphaeroides was around 35% of dry cell weight, mainly composed of vaccenic acid (C18:1, omega-7).