Concurrent maltodextrin and cellodextrin synthesis by Fibrobacter succinogenes S85 as identified by 2D NMR spectroscopy

1D and 2D NMR experiments were used to analyse the synthesis of various met abolites by resting cells of Fibrobacter succinogenes S85 when incubated wi th [1-C-13]glucose, in both extracellular and cellular media. Besides the e xpected glycogen, succinate, acetate, glucose-1-P and glucose-6-P, maltodex trins and cellodextrins were detected. Maltodextrins were excreted into the external medium. They were found to have linear structures with a maximum degree of polymerization (DP) of about 6 or 7 units. Cellodextrins were loc ated in the cells (cytoplasm and/or periplasm), and their DP was less than or equal to4. Both labelled (1-C-13 and 6-C-13) and unlabelled maltodextrin s and cellodextrins were detected, showing the contribution of carbohydrate cycling in F. succinogenes, including the reversal of glycolysis and the f utile cycle of glycogen. The mechanisms of these oligosaccharide syntheses are discussed.