Simulation of butanol production by an integrated fermentation process with gas stripping using C. pasteurianum

Petroleum is becoming a scarce resource and alternative biofuels has been studied as biobutanol. It can be blended directly with standard oil-based fuels and has the advantage of been produced from glycerol. Nowadays glycerol is an excellent source of raw material derived from biodiesel production. Clostridium pasteurianum uses glycerol as the main source of carbon but is productivity and butanol concentration is low. The main problem related to fermentation for butanol production is its toxicity to the microorganism Clostridium. Downstream process for recovering solvents in the diluted fermentation broth has two main objectives: increase butanol productivity by reducing the toxicity of solvents to the cells and minimize the energy consumption in the process. In this work a conceptual design of downstream process using gas stripping and solvent extraction was compared with traditional distillation process for butanol recovery in the broth by simulation. The raw material used in fermentation was glycerol and the main products of the metabolism of C pasteurianum were butanol and 1,3 propanediol. Gas stripping with a mixture of carbon dioxide, nitrogen and hydrogen as carrier were appliled to remove mainly 1,3 propanediol and glycerol. Then solvent extraction using acetone was applied for butanol recovery. The simulation of this process was performed using SuperPro Design®. An economic evaluation was carried out to compare this system with the conventional downstream process by distillation. Besides using glycerol as the main source of carbon, another advantage is that C. pasteurianum also produces 1,3 propanediol as a subproduct which can contribute for the economic viability of the process.