Buffer-dependent variations in alginate oligosaccharide production and their biofunctional properties in colonic fermentation.

The inclusion of a buffer in the enzymatic reaction medium can significantly affect the production and biofunctional properties of alginate oligosaccharides (AOS). This comparative study evaluated the impact of buffer addition (AOSWB) versus no buffer (AOSWoB) on the bioactivity and technofunctional properties of AOS. AOSWB showed reduced chelating activity (193.83 ± 6.29 μmol TE/g dw) and lower reducing sugars (76.92 ± 0.50 mg GE/g dw), despite treatment selection optimized via principal component analysis (PCA). AOSWoB exhibited a bidentate bridge chelation mechanism with barium, affecting bioactive and technofunctional characteristics. In an in vitro colonic fermentation model, the AOS-barium complex caused a pH decrease after 24 and 48 h of fermentation (6.19 ± 0.04 and 5.99 ± 0.03, respectively). This was reflected in antioxidant capacity (AOX) measured by DPPH and FRAP after 48 h (12.72 ± 0.68 μmol TE/g dw and 6.23 ± 1.18 μmol TE/g dw), contrasting with controls. Colonic microbiota appear to release esterases capable of deesterifying barium, causing sublethal cellular damage, adaptation via bioaccumulation, and culminating in the assimilation and metabolism of AOS to produce short-chain fatty acids (SCFA), mainly acetic acid, a precursor of ethyl acetate, the most abundant metabolite identified after 24 and 48 h of fermentation.