Although the acetone-butanol-ethanol fermentation of Clostridium acetobutylicum is currently uneconomic, the ability of the bacterium to metabolize a wide range of carbohydrates offers the potential for revival based on the use of cheap, low-grade substrates. We have investigated the uptake and metabolism of lactose, the major sugar in industrial whey waste, by C. acetobutylicum ATCC 824. Lactose is taken up via a phosphoenolpyruvate-dependent phosphotransferase system (PTS) comprising both soluble and membrane-associated components, and the resulting phosphorylated derivative is hydrolyzed by a phospho-␤-galactosidase. These activities are induced during growth on lactose but are absent in glucose-grown cells. Analysis of the C. acetobutylicum genome sequence identified a gene system, lacRFEG, encoding a transcriptional regulator of the DeoR family, IIA and IICB components of a lactose PTS, and phospho-␤-galactosidase. During growth in medium containing both glucose and lactose, C. acetobutylicum exhibited a classical diauxic growth, and the lac operon was not expressed until glucose was exhausted from the medium. The presence upstream of lacR of a potential catabolite responsive element (cre) encompassing the transcriptional start site is indicative of the mechanism of carbon catabolite repression characteristic of low-GC gram-positive bacteria. A pathway for the uptake and metabolism of lactose by this industrially important organism is proposed.The acetone-butanol-ethanol (ABE) fermentation of Clostridium acetobutylicum was a classical method to produce the commercially important solvents acetone and butanol, which operated successfully at an industrial scale in many countries during the first half of the 20th century. After the Second World War, the fermentation process declined because of the emergence of the competitive petrochemical-based synthesis of the solvents (18). Nevertheless, oil is a finite commodity and global oil prices are on the rise, and this, coupled with a general worldwide interest in exploiting renewable resources, has stimulated research on the biochemistry and physiology of solventogenic clostridia in recent years, with the aim of exploring the potential for revival of the ABE fermentation (17, 22). A major consideration in any bioconversion process is the availability of a cost-effective and high-product-yielding growth medium, whereby there is maximal conversion of the available carbon into the commercial end product. The substrate of choice in the traditional industrial ABE fermentation, molasses, accounted for more than 60% of the overall cost of the process (19). However, the clostridia are metabolically versatile with respect to carbohydrate utilization and the potential therefore exists to exploit alternative, cheaper, low-grade substrates.Several clostridial strains are able to produce solvents by fermentation of whey (21), which has been shown to be economically superior to the traditional process (19). Despite low reactor productivity, an attractive feature of these fermenta...

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SCB biodegradation and reducing sugar accumulation were remarkably increased by adding surfactant in the CBP system usingC. thermocellum.

This study explores the effect of carbon sphere preparation conditions on the morphology of the carbon spheres and the micropore development by fast potassium hydroxide activation via microwave heating. Enzymatic hydrolysis lignin is used as the precursor for carbon sphere preparation via environmentally friendly hydrothermal carbonization. The effects of various carbonization temperatures, carbonization times and reaction concentrations on the physical morphology of the carbon sphere surfaces are investigated. The Brunauer-Emmett-Teller surface area, yield and scanning electron microscopic images are used to characterize the carbon spheres. High carbonization temperatures and times result in large particle sizes, high sphericity, uniform size, and high dispersity of the carbon spheres. The best carbon spheres are obtained at 270 °C for 7 hours with a reaction concentration of 0.06 g ml−1 and a particle size of 3–6 μm. After activation, the Brunauer-Emmett-Teller surface area of the activated carbon spheres increases from 248 m2 g−1 to 1278 m2 g−1. Carbon spheres activated by treatment with fast potassium hydroxide and microwave heating can develop micropores that enhance the adsorptive capacity for small molecules, such as gases. Enzymatic hydrolysis lignin-derived carbon spheres formed via hydrothermal carbonization should be potentially sustainable materials applicable in energy and environmental fields.

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