Inflammatory bowel diseases (IBD) are chronic medical disorders characterized by recurrent gastrointestinal inflammation. While the etiology of IBD is still unknown, the pathogenesis of the disease results from perturbations in both gut microbiota and the host immune system. Gut microbiota dysbiosis in IBD is characterized by depleted diversity, reduced abundance of short chain fatty acids (SCFAs) producers and enriched proinflammatory microbes such as adherent/invasive E. coli and H2S producers. This dysbiosis may contribute to the inflammation through affecting either the immune system or a metabolic pathway. The immune responses to gut microbiota in IBD are extensively discussed. In this review, we highlight the main metabolic pathways that regulate the host-microbiota interaction. We also discuss the reported findings indicating that the microbial dysbiosis during IBD has a potential metabolic impact on colonocytes and this may underlie the disease progression. Moreover, we present the host metabolic defectiveness that adds to the impact of symbiont dysbiosis on the disease progression. This will raise the possibility that gut microbiota dysbiosis associated with IBD results in functional perturbations of host-microbiota interactions, and consequently modulates the disease development. Finally, we shed light on the possible therapeutic approaches of IBD through targeting gut microbiome.

Aims: This study aims to isolate probiotic bacteria candidates from various starter cultures and fermented foods and characterize their ability to produce γaminobutyric acid (GABA). GABA is a major inhibitory neuromediator of the central and enteric nervous systems with a role in several health disorders. Methods and Results:Fourteen strains of lactic acid bacteria were isolated from food environment and screened for the presence of the glutamate decarboxylase (gadB) gene using PCR and GAD enzymatic assay. The identified potent GABAproducers included Strep. thermophilus, Lactiplantibacillus plantarum and Lact. delbrueckii subsp. bulgaricus. GC-FID analyses confirmed the high GABA produc-

Arabinoxylan (AX) is an essential component of dietary fiber with potential prebiotic properties. However, owing to its complex structure, fermentation of AX by gut microbes is structure dependent. In this study, we evaluated the effect of bioengineered wheat AX on the metabolism and composition of gut microbiota using an in vitro fermentation model. We compared the effect of bioengineered AX with that of untreated AX and a control. Structurally modified AX did not significantly alter gut microbiome composition within 48 h of treatment; however, it enhanced the abundance of health-promoting bacterial taxa, such as Bacteroides, Bifidobacterium, Anaerofustis, and Eubacterium. Furthermore, the bioengineered AX significantly increased the level of acetate produced over 24 h. The amount of microbiota-generated butyrate was significantly increased 24 h after adding α-L-arabinofuranosidase-treated AX. AX treated with the α-L-arabinofuranosidase B25 enzyme induced higher levels of production of total short-chain fatty acids by the microbiota from four donors. The results of this study provide evidence that enzymatic structural modification of AX has the potential to modulate gut microbiome composition and metabolic activities.