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Doctoral Thesis:“ Microbial characterization of different bread-making processes and assessment of their impact on human intestinal dysbiosis and inflammatory bowel disease” 

2 July 2024

On Monday 1st July at 10:00h amMr. Aleix Lluansí read his doctoral thesis entitled: “ Microbial characterization of different bread-making processes and assessment of their impact on human intestinal dysbiosis and inflammatory bowel disease”  directed by Dr Xavier Aldeguer Manté and Dr Marc Llirós Dupré.

Thesis abstract

Inflammatory bowel disease (IBD) is a group of chronic inflammatory bowel diseases that are immune-mediated with a multifactorial aetiology. Unfortunately, there are still some gaps in its pathophysiology and, therefore, in its treatment. Different evidence has demonstrated the role of the intestinal microbiome in IBD. Furthermore, manipulation of the gut microbiome has emerged as a promising avenue for a multitude of medical conditions. In particular, prebiotics can help improve intestinal health in IBD patients through modulation of the gut microbiome.

The aim of this thesis is to describe the potential of traditional and modern breads to modulate the intestinal microbiome and improve intestinal health in patients with IBD. To do this, a characterisation of the microbial ecology throughout different bread-making processes was carried out using high-throughput sequencing of 16S and 18S ribosomal ribonucleic acid (rRNA) genomes. The impact of different ingredients and preparation methods on the final nutritional composition was evaluated. An in vitro study was conducted with faecal samples (n=6), as well as an in vivo randomised clinical trial (n=23) to assess the potential of traditional and modern breads on the gut microbiome and irritable bowel syndrome (IBS)-like symptomatology in patients with IBD. Changes in the composition of the faecal microbiota were assessed by quantitative polymerase chain reaction (qPCR) or high-throughput sequencing of the 16S rRNA gene. Specific metabolic analyses aimed at different short-chain fatty acids (SCFA) were performed. The clinical symptomatology of type IBS was assessed by means of medical questionnaires and inflammatory parameters.

The results point to a beneficial role of bread, and especially traditional bread, as a potential prebiotic complement to modulate the intestinal microbiome in the treatment of IBD and IBS-like symptoms. Firstly, it was observed that the ingredients and the methods used during the process of elaboration of bread determined the microbial composition of the masses of bread studied, but also the nutritional composition of the final forged products. In particular, a traditional pa making technique was characterised by a higher relative abundance of Lactobacillus spp. throughout the production process and a higher total dietary fibre content in the final products compared to a modern technique. Secondly, in vitro incubations of bread products with females from subjects with IBD led to a higher abundance of most of the analysed bacterial groups that are normally reduced in IBD, together with a higher production of SCFA. In particular, the most notable increases in SCFA production correlated with a higher abundance of Roseburia species. However, these changes occurred in a dose-dependent manner in relation to the amount of broiler hatched, regardless of the processing method. Finally, a dietary intervention with traditional and modern breads reduced IBS-like symptomatology in patients with IBD in the remission phase. Furthermore, the traditional bread intervention reduced the Firmicutes/Bacteroidetes ratio, which appeared to be associated with an improvement in IBS-like symptoms.

Taken together, these innovative findings suggest a potential role for bread as a prebiotic therapeutic adjunct that may help modulate the gut microbiome in the treatment of IBD and IBS-like symptoms. However, further studies are needed to confirm these results and validate their clinical implications.

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