Jiaojiao Lu,Hai Yang,Jie Hao,Chengling Wu,Li Liu,Naiyu Xu,Robert J. Linhardt,Zhenqing Zhang
Alginate is a linear and acidic polysaccharide , composed of (1 → 4) linked β- d -mannuronic acid (ManA) and α- l -guluronic acid (GulA). The ratio of ManA to GulA ( M / G ) is one of the most important factors for the application of alginate and its derivatives in various areas. In this work, a robust and accurate method was developed to analyze M / G using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The impact of hydrolysis conditions on the release patterns of ManA and GulA from alginate and its derivatives was investigated. The release patterns of ManA and GulA need to be considered separately to obtain an accurate M / G . Several hydrolysis conditions were established that released ManA and GulA completely and maintained these saccharide residues intact. The proper M / G of alginates from different sources and its derivatives could then be calculated by integration of the corresponding ManA and GulA peaks.
Biofilm-state probiotics can effectively improve their tolerance in harsh environments. Previous studies have shown that calcium alginate is an effective carrier for promoting biofilm formation, but its mechanism is unclear. Here, we show that tuning alginate molecular weight (Mw) and mannuronic/guluronic (M/G) directs Lactobacillus rhamnosus GG (LGG) biofilm formation and gastrointestinal tolerance. Our key finding is that calcium alginate beads with low Mw and low M/G alginates produce denser biofilms and superior gastrointestinal tolerance. These formulations markedly improved LGG survival in simulated challenges (gastric acid: 0.02–0.28 log CFU/g loss; bile: 1.54–2.31 log CFU/g), outperforming free cells. Mechanistic analysis revealed that low Mw and low M/G alginate matrices, with larger specific surface area, pore size, and volume, enhanced quorum-sensing autoinducer-2 signaling and subsequent protective extracellular substance synthesis, thereby improving the gastrointestinal tolerance of biofilm-state LGG. Overall, the findings emphasized that controlling alginate structure provides a rational, material-based strategy for designing advanced probiotic or bioactive delivery systems.
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