Lignocellulose-degrading enzymes from the gut of okapi and elephant

The present thesis dealt with microbial communities derived from the gut of large herbivores which efficiently degrade lignocellulose. There are essentially no protocols for the cultivation of these microbiomes, which may differ from animal to animal. Here, a first protocol was assessed on the basis of the one for giant pandas, and applied to okapi and elephant. Faecal samples were collected at the Copenhagen zoo to prepare an inoculum (the gut microbiota) fed with either cellulose, hemicellulose, lignin or animal feed. Pure substrates were used to select different microbial sub-groups, while the animal feed was used as a positive control. Fermentation kinetics were followed in terms of biogas production volume and composition, volatile fatty acids production, cell counting and pH. Some adjustments to the protocol were made for the second experiment (on okapi alone, a foregut fermenter), concerning the substrate to inoculum ratio, and improving the gut microbiome cleaning procedure. Both modifications aimed at designing a bioreactor system less intensive than the first experiment one. Following the observation of a stable foam while preparing gut microbiomes, biosurfactants and bioemulsifiers were tested. In the third experiment, the improved protocol was tested on the elephant, as a representative of a hindgut fermenter. At the end of laboratory cultivation, an attempt to identify and characterize the enzymatic fractions in bioreactors was made through an initial colorimetric and chromatographic investigation, followed by anion exchange column fractionation and SDS-Page analysis. The preliminary results highlighted that the two fermentations are clearly distinct from one another, and point to a markedly higher degradation capacity of okapi gut microbiomes. Both microbiomes were more active on hemicellulose. However, elephant gut microbiomes could produce almost uniquely acetic acid with hemicellulose substrate, an interesting observation for future applications.