Substrate-induced production and secretion of cellulases by Clostridium acetobutylicum
2004
Lopez-Contreras, A.M. | Gabor, K. | Martens, A.A. | Renckens, B.A.M. | Claassen, P (Pamela) | Oost, J van der | Vos, W. M de
Clostridium acetobutylicum ATCC 824 is a solventogenic bacterium that grows heterotrophically on a variety of carbohydrates, including glucose, cellobiose, xylose, and lichenan, a linear polymer of beta-1,3- and beta-1,4-linked beta-D-glucose units. C. acetobutylicum does not degrade cellulose, although its genome sequence contains several cellulase-encoding genes and a complete cellulosome cluster of cellulosome genes. In the present study, we demonstrate that a low but significant level of induction of cellulase activity occurs during growth on xylose or lichenan. The celF gene, located in the cellulosome-like gene cluster and coding for a unique cellulase that belongs to glycoside hydrolase family 48, was cloned in Escherichia coli, and antibodies were raised against the overproduced CelF protein. A Western blot analysis suggested a possible catabolite repression by glucose or cellobiose and an up-regulation by lichenan or xylose of the extracellular production of CelF by C. acetobutylicum. Possible reasons for the apparent inability of C. acetobutylicum to degrade cellulose are discussed.
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