A novel integrated fermentation/recovery system for butanol production by Clostridium acetobutylicum

Intensive butanol production was carried out by immobilized cells of Clostridium acetobutylicum in a novel continuous fermentation system. The fermentation system consisted of four packed bed biofilm reactors (PBBR) connected in series. The novelty of the proposed system is: i) the use of a novel stagewise simulated moving bed (SMB) design/operational mode; ii) the integration of the reaction and the product recovery sections. The SMB operational mode was accomplished by equipping the PBBR with manifolds and time-actuated switching valves. PBBR integration with the product recovery section was also tested. An adsorption column was operated between the 3^rd and 4^th reactor of the series.

The tuning of the PBBR system overall dilution rate (D_OV) allowed to maximize: i) sugar conversion (D_OV <0.150 h⁻¹); ii) butanol concentration (0.650 h⁻¹<D_OV<0.900 h^-1); iii) butanol productivity (13.0 g/Lh at D_OV=0.900 h^-1).

The PBBR system was upgraded by integrating it with an in-line adsorption column and it guaranteed a twofold increase in butanol productivity (up to 22 g/Lh) and an average butanol concentration close to 24.0 g/L.