ABE fermentation

Qureshi, N., and Maddox, I. S., Reactor Design for the ABE Fermentation Using Cells of Clostridium acetobutylicum Immobilized by Adsorption onto... 

A narrow beam, attainable with Raman, was used by Schuster et al.4 to characterize the population distribution in Clostridium cultures. The technique was applied to the acetone-butanol (ABE) fermentation process in which the solventogenic Clostridia go through a complex cell cycle. After drying the cells on calcium fluoride carriers, single-cell spectra were obtained. Cells of different morphology showed different spectra. A number of cell components could be detected and varied in quantity. The approach was seen to be far faster than conventional methods. 

Schuster et al. reported work on monitoring a complex ace-tone-butanol-ethanol (ABE) fermentation system.22 They looked at the qualitative nature of the biomass as well as the solvents present in the liquid phase. A hierarchical cluster analysis was performed on samples from various times of the fermentation. The clusters were then classified using classical markers and analyses. The resultant table, combining qualitative interpretation and quantitative results, shows an interesting mosaic of the system over time. Total solvents, optical density, and butyric acid are given as numeric values in either absorbance units of g/1. 

Corn steep liquor (CSL), a byproduct of the com wet-milling process, was used in an immobilized cell continuous biofilm reactor to replace the expensive P2 medium ingredients. The use of CSL resulted in the production of 6.29 g/L of total acetone-butanol-ethanol (ABE) as compared with 6.86 g/L in a control experiment. These studies were performed at a dilution rate of 0.32 hr1. The productivities in the control and CSL experiment were 2.19 and 2.01 g/(Lh), respectively. Although the use of CSL resulted in a 10% decrease in productivity, it is viewed that its application would be economical compared to P2 medium. Hence, CSL may be used to replace the P2 medium. It was also demonstrated that inclusion of butyrate into the feed was beneficial to the butanol fermentation. A control experiment produced 4.77 g/L of total ABE, and the experiment with supplemented sodium butyrate produced 5.70 g/L of total ABE. The butanol concentration increased from 3.14 to 4.04 g/L. Inclusion of acetate in the feed medium of the immobilized cell biofilm reactor was not found to be beneficial for the ABE fermentation, as reported for the batch ABE fermentation. 

Index Entries ABE fermentation butanol Clostridium acetobutylicum fibrous bed bioreactor dilution rate. 

Fig. 2. Kinetics of continuous ABE fermentation at various dilution rates and pH 4.3. Glucose and OD are on the right axis acetone, butanol, ethanol, acetate, and butyrate are on the left axis. (A) Reactor L (B) reactor R.

Optimizing the ABE fermentation process has long been the aspiration of more than a century of research. Conventionally, the profitability of fermentation is influenced by the type and concentration of substrate, dilution rate, pH, culture medium, and product recovery. Even using cell recycle, cell immobilization, or extractive fermentation to increase cell density and productivity, the yield of the combined ABE production never exceeded 0.44 g/g (13-15). 

Regulation of Solvent Formation in C. acetobutylicum 345 Genetic Tools for Clostridial Species 346 Industrial Application of ABE Fermentation 353 Acknowledgments 355 References 355... 

One of the earliest unconfirmed examples of an ABE fermentation phage infection concerned an abnormal fermentation at the CSC plant in Terre Haute, USA, using maize mash as substrate for a C. acetobutylicum strain [32]. In this instance, the sluggish fermentation lasted for about 1 year and halved the solvent yield. CSC expended considerable efforts into the investigation of the cause of this abnormal fermentation performance and developed a number of countermeasures for preventing its recurrence. These included the use of phage-immunized clostridial... 

C. acetobutylicum is the model microorganism to study clostridial ABE fermentation. The respective biphasic metabolism is similar to other solventogenic clostridial species (Table 9.1, see Section 9.5). The fermentation starts with uptake of the substrate (e.g., hexoses and pentoses). Sugars are metabolized to... 

ABE Fermentation of Solvent-Producing Clostridium Strains 337 Table 9.1 General GenBank features of genomes of solventogenic clostridia. 

Liao et al. [82] have recently presented a system-level computational framework for ABE fermentation by C. acetobutylicum and combined metabohc... 

The ABE fermentation is an important industrial biotechnological process in which carbohydrate-based feedstocks are readily converted into acetone and butanol by solventogenic clostridia under anaerobic conditions. 

The ABE fermentation process was first developed by C. Weizmann at Manchester University in 1912. Commercial production quickly spread to the United States and then worldwide during the First and Second World Wars first to produce acetone for ammunitions and then later to produce butanol for paint lacquers. The fermentation process fell out of favor in the United States and Europe in the 1950s when renewable solvents could no longer compete with their synthetic equivalents on price. Some production, via fermentation, continued in China, Russia, and South Africa until the early 1980s [54]. 

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