Kinetics modeling of butanol production by IBE fermentation of an industrial sugary material using Clostridium beijerinckii DSM 6423

Biobutanol is considered an attractive biofuel. It has superior properties to ethanol: higher energy content, less volatile and explosive, does not require modification of engines using gasoline and is less corrosive. It can be produced by acetone–butanol–ethanol (ABE) fermentation. The production of isopropanol instead of acetone, which is corrosive, makes the produced mixture of solvents (IBE) to be used as fuel. The main aim of this work was to evaluate the production of butanol and isopropanol from a mixture of industrial juices of sugarcane (75%) and sweet sorghum (25%). Fermentation assays were done in bottles using Clostridium beijerinckii DSM 6423. At 47 h of incubation, fermentation ceased, when the butanol concentration reached 6.4 g/L (11.4 g/L total ABE) because of the toxic effect of butanol. The butanol production was modelled at macroscopic level using kinetic models with and without product inhibition to describe the cell growth, the sugar (as glucose) consumption and the butanol production. MatLab® software was used to estimate parameters values that produce the best fit between the experimental observation and the simulated response. The parameters determined were: μ_máx (maximum specific cell growth rate), K_s (glucose affinity constant), Y_X/S (biomass per glucose yield), Y_P/S (butanol per glucose yield), K_p (butanol growth inhibition constant) and k_d (specific cell death rate). Clostridium beijerinckii DSM 6423 proved to be a promising strain for isopropanol and butanol production of a natural sugary substrate. The kinetic model with product inhibition predicted experimental data with a correlation coefficient (ρ) higher than 0.9.