Abstract/Summary

Abstract for volume 1: Oligofructose and inulin are a class of prebiotics referred to as inulin-type fructans. Due to their physiochemical properties inulin-type fructans can function as fat and sugar replacers while still providing prebiotic dosages. Yet, can be subject to degradation depending on the processing parameters used during production. Additionally, one aspect frequently overlooked when designing prebiotic food-based supplementation studies is the presence of other bioactive compounds within the matrix including polyphenol and arabinoxylans, each of which can alter microbial composition. As a results, there is interest on whether the food matrix matters in the supplementation of inulin-type fructans and effects on microbial composition. To address this question we firstly summarised the literature regarding previous inulin-type fructan food-based supplementation studies. The findings suggesting that the bifidogenic effect of inulin-type fructans is unaltered as a result of the food matrix, but due to differences in study protocols no definitive conclusions can be made based on these findings. To test our working hypothesis that the bifidogenic effect of inulin-type fructans is unaltered as a result of the food matrix we conducted a 10-day 4-arm parallel, randomised, non-placebo-controlled non-inferiority trial following a standardised protocol. Similar increases in bifidobacteria were detected across all four interventions (all P ≤ 0.05). Significant differences in Roseburia and Faecalibacterium were detected between shortbread, and milk chocolate interventions (all P ≤ 0.05). Stool consistency was only significantly higher in the pure inulin intervention (P ≤ 0.05). No differences in stool frequency or gastrointestinal sensations were detected between interventions with exception of feeling of fullness in pure inulin compared to the rice drink intervention (P ≤ 0.05). In conclusion, the findings of this thesis suggest that irrespective of the food matrix the bifidogenic effect of inulin-type fructans is unaltered. Yet, the compositional nature of the food matrix may have implications regarding stimulating changes in the wider microbiota. Abstract for volume 2: There is much interest in whether blending inulin-type fructans with other novel oligosaccharides including β-glucan and 2’fuscosyllactose can result in a more controllable approach in manipulating microbial composition and resulting metabolites. Additionally, anxiety and depression are two of the biggest mental health issues worldwide. Due to the relationship existing between the gut and the brain one way to potentially influence mood state may be through targeted manipulation of the gut microbiota. Yet, much remains unknown about the ability of prebiotics to influence mood state. To test our hypothesis that blending the prebiotic inulin-type fructans with β-glucan and 2’fuscosyllactose would result in a more controllable approach in targeted manipulation of the gut microbiota and resulting metabolites. We firstly conducted in vitro batch culture fermentations monitoring changes in microbial load, organic acid and neurotransmitter production. Results demonstrating that combinations of oligofructose/β-glucan and oligofructose/2’fuscosyllactose increased numbers of Roseburia, Clostridum cluster IX and faecalibacterium. Along with sustained propionate and butyrate production compared to sole supplementation (P ≤ 0.05). While sole oligofructose and oligofructose/2’fucosyllactose combination induced physiologically relevant increases in γ-aminobutyric acid production (P ≤ 0.05). Next, we conducted a 5-week, 4-arm parallel, randomised placebo-controlled trial looking for difference in microbial composition and mood state parameters using sole oligofructose and 2’fucosyllactose and combination of oligofructose/2’fucosyllactose as interventions. Considerable differences in microbial composition were detected between substrates with both oligofructose and oligofructose/2’fucosyllactose combinations inducing large microbial shifts in Bifidobacterium, Roseburia and faecalibacterium (P ≤ 0.05). Along with remarkable improvements in mood state parameters (P ≤ 0.05) compared to sole 2’FL supplementation. In conclusion, the results suggests of this thesis suggest that combinations of oligofructose with β-glucan and 2’fucosyllactose can provide a more controlled approach to targeted manipulation of the gut microbiota and resulting metabolites. Along with inducing meaningful improvements in microbial composition and mood state parameters in vivo.