Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Hubei University of Technology, Nanli Road, Wuhan 430068, P. R. China.
Glyn O. Phillips Hydrocolloid Research Centre, School of Life and Health Sciences, Hubei University of Technology, Nanli Road, Wuhan 430068, P. R. China.
Food Funct. 2024 Jul 29;15(15):8128-8142. doi: 10.1039/d4fo00934g.
The degradation of sodium alginate by human gut microbiota was found to be retarded calcium cross-linking in our previous study. We hypothesized that the guluronic acid block (GB) on the alginate molecule might be the key structural region affecting alginate degradation by the gut microbiota when cross-linked with calcium. This study aims to prove this hypothesis by studying the structural features of the cross-linked GB on its fecal fermentation behaviors concerning the aspects of total carbohydrate contents, monosaccharide contents, short-chain fatty acids production, calcium state variations, and structural variations. Herein, GB isolated from sodium alginate was cross-linked under ranges of molar ratios of [Ca]/[-COOH] that further restricted the degradation by gut microbiota similar to the cross-linked alginates. First, total carbohydrate contents, short-chain fatty acids production, monosaccharides contents, and calcium state analyses confirmed that the degradation of GB by gut microbiota was restricted by calcium cross-linking. Furthermore, the tracking analysis of structural variations during fermentation revealed that the "granules" structure could further restrict degradation by the gut microbiota, leaving more cross-linked GB fragments surviving in comparison to the "networks" structure. In addition, showed a significant positive correlation to the "cross-linking porosity ( = 0.825, < 0.001), which supported our previous findings on fermentation behaviors of cross-linked alginate. Together, guluronic acid blocks are the key structural regions that retard the degradation of sodium alginate by the gut microbiota when cross-linked with calcium.
在我们之前的研究中发现，肠道微生物群会减缓海藻酸钠的降解，而这种降解会受到钙交联的影响。我们假设，当海藻酸钠分子与钙交联时，其分子上的古洛糖醛酸块（GB）可能是影响肠道微生物群降解海藻酸钠的关键结构区域。本研究旨在通过研究交联 GB 的结构特征，来证明这一假设，从粪便发酵行为的角度研究其总碳水化合物含量、单糖含量、短链脂肪酸生成、钙状态变化和结构变化。在此，将从海藻酸钠中分离出的 GB 进行交联，范围为[Ca]/[-COOH]的摩尔比，类似于交联海藻酸钠，进一步限制了肠道微生物群的降解。首先，总碳水化合物含量、短链脂肪酸生成、单糖含量和钙状态分析证实，肠道微生物群对 GB 的降解受到钙交联的限制。此外，发酵过程中结构变化的跟踪分析表明，“颗粒”结构可以进一步限制肠道微生物群的降解，与“网络”结构相比，留下更多交联的 GB 片段存活。此外，还与“交联孔隙率（ = 0.825， < 0.001）呈显著正相关，这支持了我们之前关于交联海藻酸钠发酵行为的发现。综上所述，古洛糖醛酸块是肠道微生物群在与钙交联时减缓海藻酸钠降解的关键结构区域。
