An in vitro study of the interactions of bacteria from the human colon.

Duncan, Alison J.

Abstract

An in vitro model system inoculated with human faeces was used to study the fermentation of mixtures of bran, cabbage, turnip, carrot and apple dietary fibres. The results suggested that the mixture in which a dietary fibre is supplied influenced its digestibility even though the chemical composition of the different mixtures was very similar. The pentose fractions of the fibre were the least digestible. Starch-, xylan- and pectin-degrading bacteria were enumerated and the majority of isolates were capable of more than one activity. These results highlight the potential for metabolic diversity amongst the predominant bacteria in vivo. Total numbers of bacteria were relatively constant throughout the experiments and close to estimates of bacterial numbers in the human colon. The volatile fatty acids, acetate, propionate and butyrate were the major bacterial end-products and were produced in molar ratios close to those observed in vivo. Small amounts of methane and hydrogen were produced during all experiments but there was no evidence of a product-precursor relationship. It is postulated that the production of acetate from H2 and CO2 during homoacetic acid fermentation was the major hydrogenotrophic reaction taking place. Nitrate was reduced to N2 during dissimilatory nitrate reduction and nitrite only appeared as a transient intermediate when nitrate concentrations increased. Ammonia was always produced in the fermentor as a by-product of the fermentation of amino acids. Sulphate was reduced to H2S and this process was inhibited by increased concentrations of nitrate.

Citation

DUNCAN, A.J. 1986. An in vitro study of the interactions of bacteria from the human colon. Robert Gordon's Institute of Technology, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-1993268

• Thesis Type: Thesis
• Deposit Date: Aug 2, 2024
• Publicly Available Date: Aug 2, 2024
• DOI: https://doi.org/10.48526/rgu-wt-1993268
• Public URL: https://rgu-repository.worktribe.com/output/1993268
• Award Date: Aug 31, 1986