The effect of heat-shocking on batch fermentation by Clostridium beijerinckii NRRL B592.

In spite of the large-scale industrial use of the acetone-butanol fermentation process earlier this century (until 1983 in South Africa), very little has been published on the inoculum preparation techniques required for successful fermentation using these bacteria. In particular, heat-shocking has often been referred to as "useful" but no quantitative data are available. Data presented in this paper demonstrate and quantify the effect of heat-shocking on batch fermentation yields using one organism capable of this fermentation.

The acetone-butanol fermentation in pilot plant and pre-industrial scale.

A summary of literature data concerning pilot or preindustrial scale trials of the acetone-butanol fermentation throughout its history is given. The recent pilot plant trials in Austria are also described for the first time. Some aspects of the current development of the acetone-butanol fermentation in general, especially from a technical point of view are also discussed.

Solvent production by Clostridium beijerinckii NRRL B592 growing on different potato media.

Very good solvent formation rates were observed when Clostridium beijerinckii NRRL B592 was cultivated on different whole potato media. The increase in whole potato concentration contributed to the increased final solvent concentrations, while the addition of yeast extract or mineral salts gave negative effects. To obtain good solvent productivities and high final solvent concentrations during batch fermentation, no enzymatic hydrolysis of the potato starch was necessary, indicating high activity of the clostridial amylases produced by the strain applied.

Long-Term Continuous Cultivation of Clostridium beijerinckii in a Two-Stage Chemostat with On-Line Solvent Removal.

A two-stage continuous cultivation experiment with Clostridium beijerinckii NRRL B592 is described. This strain maintained its ability to produce neutral solvents (acetone, n-butanol, and ethanol) at an overall dilution rate of 0.13 h(sup-1) and achieved an average overall solvent concentration of 9.27 g/liter and an overall solvent productivity of 1.24 g/liter/h for more than 100 overall retention times. The experiment was performed without pH control on a semisynthetic medium containing yeast extract, and product inhibition was the limiting factor. Solid carrier material was present in both stages, and the solvent productivity in both stages was similar. A membrane evaporation module integrated into the recirculation loop of a second-stage bioreactor after 2,166 h increased solvent productivity and improved the yield of solvents by about 40%. The membrane reduced the concentration of solvents, which would otherwise inhibit the fermentation. Additionally, the integrated membrane evaporation dampened metabolic oscillations, which are characteristic of continuous cultivation of clostridia. It was also demonstrated that a moderate concentration buildup (approximately 30% of bioreactor inflow) caused by water flux through the membrane caused no detrimental effects to the bacterial cells. However, much higher water fluxes through the membrane, associated with a much more dramatic increase in the concentration of salts in the medium, did appear to favor cell degeneration.