Abstract
Clostridium acetobutylicum ATCC 824 is a solventogenic, obligate anaerobic bacterium that can grow on various types of carbohydrates and are capable of producing spores. In the present study, Clostridium acetobutylicum was successfully grown on TYA medium (tryptone, yeast, acetate medium) containing two different carbon sources, glucose and sucrose coupled with the production of acids (butyric and acetic acid) and solvents, ABE (acetone, butanol and ethanol). An investigation was undertaken to determine the impact of the two types of carbon sources on the solvent production and growth of Clostridium acetobutylicum. HPLC and GC analysis revealed the amount of acids and solvents produced respectively, as well as the amount of unutilized sugars. The amount of combined ABE produced on glucose (0.19g/l A, 0.39g/l B, 0.06g/l E) was higher than on sucrose as carbon source (0.15g/l A, 0.30g/l B, 0.03g/l E). The colony forming units of Clostridium acetobutylicum grown on glucose (4.70 x 105 units/ml) was higher than on sucrose (0.1 x 105) as judged by dilution spread plating on agar. Hence, Glucose was confirmed as the carbon source characterized by the best performance for solvents production and growth of the bacterium. The whole production process on both glucose and sucrose was observed to mainly influence the production of butanol with the concentration of 0.39g/l and 0.30g/l respectively, over the production of other solvents. Higher amount of solvents was produced at lower pH in both cultures with the different carbon sources. Wet-mounts, gram stain and endospore stain were used to determine the motility, type and sporulation of Clostridium acetobutylicum respectively. Acidogenic phase which seems to couple with the growth of vegetative cells, results into production of acetic and butyric acids. Solventogenic phase commences with a drop in pH and is accompanied by the onset of sporulation.
Highlights
Clostridium acetobutylicum ATCC 824 is an obligate anaerobe, Gram positive solventogenic bacterium that grows heterotrophically on various carbohydrates such as glucose, cellobiose and xylose
The objective of this study is to investigate the cell growth and solvent production by the bacterium Clostridium acetobutylicum in relation to the different types of carbon sources used as substrates and to determine the factors that can affect the switching of phase from acidogenesis to solventogenesis
Clostridium acetobutylicum ATCC 824 spores stock culture was germinated in Reinforced Clostrida Medium (RCM; Oxoid): The spores (0.5 – 1 ml) stock was heat shocked in sterile glass tube at 800C for 10 minutes and immediately transferred to 20ml RCM in the anaerobic workstation
Summary
Clostridium acetobutylicum ATCC 824 is an obligate anaerobe, Gram positive solventogenic bacterium that grows heterotrophically on various carbohydrates such as glucose, cellobiose and xylose. This bacterium is best known for its fermentative pathway which results in production of commercially significant solvents; butanol, acetone, and ethanol [1]. Members of the genus Clostridium include C. difficile, C. pefringens and C. botulinum: these are toxin producing species with much medical significance. Members of the genus Clostridium produce terminal endospores, which confer a high degree of resistance to heat, desiccation and other environmental challenges, they can survive harsh environment over long periods of time [2]. Sporulation is triggered by low pH, the presence of carbohydrates and at times a quorum sensing mechanism at high population densities [4, 5]
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