Continuous cultivation of photosynthetic bacteria for fatty acids production

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).