Biobutanol production from C5/C6 carbohydrates integrated with pervaporation: experimental results and conceptual plant design.

In this study, a simulated lignocellulosic hydrolyzate was used in a continuous two-stage fermentor setup for production of acetone, butanol and ethanol. An organophilic pervaporation unit was coupled to the second fermentor. The dilution rate in the first fermentor was kept constant at 0.109 h(-1), while the dilution rate in the second fermentor was gradually decreased from 0.056 to 0.020 h(-1). Glucose was completely consumed, while 61% of the xylose was consumed at the lowest dilution rate, leading to an overall solvent productivity of 0.65 g L(-1) h(-1) and a high concentration of 185 g kg(-1) solvents in the permeate in the last fermentation zone during 192 h. Based on the experimental results, a process integrated with organophilic pervaporation was conceptually designed and compared with a base-case. Chemcad simulations indicate an energy reduction of ~50% when organophilic pervaporation is used. This study also demonstrates significant reductions in process flows and energy consumption by the use of organophilic pervaporation as in situ product recovery technology.

Integrated bioprocess for long-term continuous cultivation of Clostridium acetobutylicum coupled to pervaporation with PDMS composite membranes.

A continuous cultivation of Clostridium acetobutylicum ATCC 824 is described using a two-stage design to mimic the two phases of batch culture growth of the organism. A hydrophobic pervaporation unit was coupled to the second fermentor containing the highest solvent titers. This in situ product recovery technology efficiently decreased butanol toxicity in the fermentor while the permeate was enriched to 57-195 g L(-1) total solvents depending on the solvent concentrations in the fermentor. By the alleviation of product inhibition, the glucose concentration could be increased from 60 to 126 g L(-1) while the productivity increased concomitantly from 0.13 to 0.30 g L(-1)h(-1). The continuous fermentation was conducted for 1172 h during which the pervaporation was coupled to the second fermentor for 475 h with an average flux of 367 g m(-2)h(-1). The energy consumption was calculated for a 2 wt.% n-butanol fermentation broth and compared with the conventional process.