Starch Utilisation by the Beneficial Microbiota Genus Bifidobacterium for Improved Health Outcomes

Millar, Molly (2023) Starch Utilisation by the Beneficial Microbiota Genus Bifidobacterium for Improved Health Outcomes. Doctoral thesis, University of East Anglia.

[thumbnail of 2023MillarMPhD.pdf]
Download (18MB) | Preview


The gut microbiome is an important axis of health and disease. A key function of gut bacteria is fermentation of dietary fibre producing short chain fatty acids (SCFA) which directly benefit host health. Fibre includes forms of starch which are resistant to digestion. Degraders of resistant starch (RS) include Bifidobacterium, a genus of beneficial, Gram-positive, anaerobic commensals. They first colonise the infant gut as degraders of human milk sugars and reduce in relative abundance with age as available substrates decline. Adequate fibre and RS intake is associated with higher bifidobacterial abundance and is generally regarded as a marker of a ‘healthy gut microbiome’.

This thesis explored the relationship between starch hydrolysis capabilities of bifidobacteria and their associated niche e.g. infant or adult microbiome. Bifidobacterium isolates were assessed for RS degrading phenotype using a range of RS structures. The ecological impacts of strain supplementation combined with a high-amylose maize starch (‘synbiotic’) using an in vitro fermentation model of the infant and adult microbiome were tested. The biomolecular interface between strong degrader Bifidobacterium pseudolongum and RS was researched using genomic, transcriptomic, proteomic, and metabolomic investigation.

Bifidobacterium strains presented niche-specific starch degradation phenotypes: pre-weaning species were non-degraders; transitional (weaning) species were moderate utilisers; and strong degraders were associated with the adult or ruminant microbiota. A large gene cluster with novel protein functions (amylase flanked by starch binding modules, including RS-binding module CBM74) was discovered in primary degrader B. pseudolongum which was found to be upregulated in the presence of starch. The structure-function relationship between RS and Bifidobacterium with regards to SCFA production was starch structure and strain specific. New information in this field could aid in precision microbiome modulation, development of next generation synbiotics, or influence our understanding of how RS in foods could enhance Bifidobacterium levels in the human gut microbiota.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 05 Sep 2023 10:49
Last Modified: 05 Sep 2023 10:49


Downloads per month over past year

Actions (login required)

View Item View Item