Cellobiose Clostridium thermocellum

We next tried to provide a-GlP, not from sucrose, but from cellobiose by using CBP. When CBP from Clostridium thermocellum (Kim et al., 2002) and GP were incubated with cellobiose in the presence of Pi and maltooligosac-chride primer, linear a-1,4 glucan was synthesized wth a yield (38.6 %) that was much lower than in the SP-GP method (Ohdan et al., 2007). To improve the yield of amylose, mutarotase and glucose oxidase were added to the initial reaction mixture with the expectation that they would remove the glucose derived from the CBP reaction and consequently shift the equilibrium state to phosphorolysis. The yield of amylose was increased to 64.8% (Ohdan et al., 2007). 

Kim, Y. K., Kitaoka, M., Krishnareddy, M., Mori, Y., and Hayashi, K. 2002. Kinetic studies of a recombinant cellobiose phosphorylase (CBP) of the Clostridium thermocellum YM4 strain expressed in Escherichia coli. J. Biochem., 132, 197-203. 

Similarly, the choice of enzymes in pathway design is of importance. In the case of the conversion of cellulose to starch, cellobiose phosphorylase and a-glucan phosphorylase are responsible for reversibly eonverting from eello-biose to amylose or vice versa. It was found that a-gluean phosphorylase from potato is a key enzyme to drive the reaction toward starch synthesis. In contrast, the same enzyme from Clostridium thermocellum eannot generate amylase from cellobiose because it prefers the starch degradation direetion. ... 

The synthesis of extracellular cellulase activity by three strains of Clostridium thermocellum growing on cellulose has been shown to be directly related to the degradation of cellulose and to the growth of the bacteria. Cellulase was not detected when the cells grow on cellobiose. The activities of the exo-D-glucanase (pH optimum 5.2, temperature optimum 65 °C) and e do-D-glucanase (pH optimum 5.4, temperature optimum 64 °C) were compared. o-Glucose and cellobiose were released when the crude cellulase acted on cellulose, cellotetraose, and cellotriose in vitro. 

Wood BE, Ingram LO (1992) Ethanol production from cellobiose, amorphous cellulose, and crystalline cellulose by recombinant Klebsiella oxytoca containing chromosomally integrated Zymomonas mobilis genes for ethanol production and plasmids expressing thermostable cellulase genes from Clostridium thermocellum. Appl Environ Microbiol 58 2103-2110... 

An analogous synthesis of cellobiose from o-D-glucose i-phosphate and D-glucose by an enzyme obtained from Clostridium thermocellum has been reported . ... 

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