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Appl. Environ. Microbiol., Feb 1997, 665-669, Vol 63, No. 2
G Maglione, JB Russell and DB Wilson
Growing cultures of Fibrobacter succinogenes S85 digested cellulose at a
rapid rate, but nongrowing cells and cell extracts did not have detectable
crystalline cellulase activity. Cells that had been growing exponentially
on cellobiose initiated cellulose digestion and succinate production
immediately, and cellulose-dependent succinate production could be used as
an index of enzyme activity against crystalline cellulose. Cells incubated
with cellulose never produced detectable cellobiose, and cells that were
preincubated for a short time with thiocellobiose lost their ability to
digest cellulose (competitive inhibition [K(infi)] of only 0.2 mg/ml or
0.56 mM). Based on these results, the crystalline cellulases of F.
succinogenes were very sensitive to feedback inhibition. Different
cellulose sources bound different amounts of Congo red, and the binding
capacity was HCl-regenerated cellulose > ball-milled cellulose >
Sigmacel > Avicel > filter paper. Congo red binding capacity was
highly correlated with the maximum rates of metabolism of cellulose
digestion and inversely related to K(infm). Congo red (250 (mu)g/ml) did
not inhibit the growth of F. succinogenes S85 on cellobiose, but this
concentration of Congo red inhibited the rate of ball-milled cellulose
digestion. A Lineweaver-Burk plot of ball-milled cellulose digestion rate
versus the amount of cellulose indicated that Congo red was a competitive
inhibitor of cellulose digestion (K(infi) was 250 (mu)g/ml).
Copyright © 1997, American Society for Microbiology
Kinetics of Cellulose Digestion by Fibrobacter succinogenes S85
Section of Microbiology and Section of Biochemistry, Cornell University, and Agricultural Research Service, U.S. Department of Agriculture, Ithaca, New York 14853
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