Fig. 2

Volumetric productivities in time during continuous methanol-based propionate elongation in an anaerobic open-culture reactor at 309 K. The production of protons in mmol/day is also shown ( ). The vertical lines indicate the major changes in the setup: change of the hydraulic retention time (HRT) from 42 to 95 h ( ), pH change from 6.3 to 5.8 ( ) and pH change from 5.8 to 5.5 ( )