Hang, XiaoGong, Zhijin2025-01-232025-01-232024-0910.7275/55367https://hdl.handle.net/20.500.14394/55367Carrageenan (CGN) is an undigested food additive extracted from red seaweed that has been used for hundreds of years. Whether this undigested marine-derived polysaccharide will be further utilized by human microbiota remains a mystery. Fermentation of dietary polysaccharides in the human lower gut plays a vital role in maintaining the functionality and completeness of the bacterial population and host cells (1). This study aims to investigate the degradation of kappa-carrageenan (k-CGN) by human gut microbiota and its potential pro-inflammatory effects. To understand whether k-CGN was broken down by human microbiota among different individuals, seven fecal samples were collected and made into fecal slurry for in vitro fermentation. Fermentation using k-CGN as the sole carbon source happened under anaerobic conditions for 48 hours, then at 0h, 24h, and 48h time points, pH value, and total carbohydrate content were measured. Fermented samples were then cultivated on a selective medium and purified into single-strain bacteria. To determine the pro-inflammatory effect of degraded kappa-carrageenan, a supernatant of fermented samples was used to treat RAW 264.7 cells, and the level of Nitric oxide (NO) production was measured to evaluate the inflammatory response triggered by degraded k-CGN in comparison to glucose. Results of the fermentation study revealed that kappa-carrageenan can be degraded by human microflora but has individual variability. In seven samples, 3 showed evidence of breaking down k-CGN by decreasing pH value and total carbohydrate content after fermentation. The reduction of pH was due to bacteria utilizing carrageenan and producing acids. However, degradation of k-CGN by isolated single strains of bacteria remained unclear as no significant reduction of pH and total sugar content could be observed after fermentation. Results of the cell study indicated after fermentation by fecal bacteria, degraded k-CGN has a pro-inflammatory effect shown by the significant increase in inflammatory markers (e.g., nitric oxide production) in cells treated with fermentation supernatant.Thesis (Open Access)https://orcid.org/0009-0001-5686-0507