(592a) Parameters Affecting Butanol Production Via the Fermentation of Biodiesel Derived Crude Glycerol by Clostridium Pasteurianum ATCC™ 6013

Significant growth of the biodiesel industry, has led to excess accumulation of crude glycerol, which has become a waste byproduct, due to its impure nature. The crude glycerol is produced at 10 wt % during the process, and it contains methanol, heavy metals and high salt concentration. Purification is costly for the biodiesel producers and has encouraged development of other new methods to use crude glycerol for generating valuable chemical compounds. We have recently reported an average yield of 0.22 g/g of butanol using crude glycerol, in comparison to a yield of 0.24 g/g using pure glycerol, during the bioconversion of glycerol by Clostridium pasteurianum. In this research, we have investigated different parameters affecting growth and solvent production using either crude glycerol or pure glycerol as the sole carbon source. The methanol and high salt content of the crude glycerol can have an inhibitive effect on growth and solvent production. In this research study, the effect of methanol and salts were conducted by adding them at different concentrations to the media containing pure glycerol. The concentration of methanol and salts used in the experiments corresponded to the various concentrations of them in crude glycerol. We also studied the effect of the addition of co-products such as sodium acetate and sodium butyrate, and iron, a media component, on butanol production. The addition of iron and co-products were carried to observe their effect on the final yield of butanol, along with pH stabilization of the cultures by the latter. In batch fermentation, as the initial glycerol concentration is increased, there is an also increase in the production of butanol. Butanol, at higher concentrations, is toxic to the cells, the cell membrane in particular. So it is of most importance to develop strains that are tolerant to higher butanol concentrations. Here, we report the development of butanol tolerant strains and their use to convert glycerol at higher concentrations. Apart from these studies, this presentation will also discuss microarray analysis comparing gene transcription during the metabolism of crude and pure glycerol. Thus, overall this study resulted in the knowledge of some of the most crucial parameters for butanol production from crude glycerol.