C-13 and H-1 NMR study of cellulose metabolism by Fibrobacter succinogenesS85

Fibrobacter succinogenes S85, a cellulolytic rumen bacterium, is very effic ient in degrading lignocellulosic substrates and could be used to develop a biotechnological process for the treatment of wastes. In this work, the me tabolism of cellulose by F. succinogenes S85 was investigated using in vivo C-13 NMR and C-13-filtered spin-echo difference H-1 NMR spectroscopy. The degradation of unlabelled cellulose synthesised by Acetobacter xylinum was studied indirectly, in the presence of [1-C-13]glucose, by estimating the i sotopic dilution of the final bacterial fermentation products (glycogen, su ccinate, acetate). During the pre-incubation period of F. succinogenes cell s with cellulose fibres, some cells ('non-adherent') did not attach to the solid material. Results for 'adherent' cells showed that about one fourth o f the glucose units entering F. succinogenes metabolism originated from cel lulose degradation. A huge reversal of succinate metabolism pathway and pro duction of large amounts of unlabelled acetate which was observed during in cubation with glucose only, was found to be much decreased in the presence of solid substrate. The synthesis of glucose 6-phophate was slightly increa sed in the presence of cellulose. Results clearly showed that 'non-adherent ' cells were able to metabolise glucose very efficiently; consequently the metabolic state of these cells was not responsible for their 'non-adherence ' to cellulose fibre. (C) 2000 Elsevier Science B.V. All rights reserved.