The properties of biofilm EPS are determined by the multiple interactions between its constituents and the surrounding environment. Because of the high complexity of biofilm EPS, its constituents' characterisation is still far from thorough, and identification of these interactions cannot be done yet. Therefore, we use gels of bacterial alginate-like exopolysaccharides (ALEs) as a model component for biofilm EPS in this work. These gels have been examined for their cohesive properties as a function of CaCl₂ and KCl concentration. Hereto, ALE gel layers were formed on membranes by dead-end filtration of ALE solutions. Accumulation of the cations Ca²⁺ and K⁺ in the gels could be well predicted from a Donnan equilibrium model based on the fixed negative charges in the ALE. This suggests that there is no specific binding of Ca²⁺ to the ALE and that on the time scale of the experiments, the Ca²⁺ ions can distribute freely over the gel and the surrounding solution. The concentration of fixed negative charges in the ALE was estimated around 1 mmol/g VSS (volatile suspended solids, organic mass) from the Donnan equilibrium. Moreover, an accumulation of H⁺ was predicted. Gels with more CaCl₂ in the supernatant were more compact and bore a higher osmotic pressure than those with less CaCl₂, revealing the role of Ca²⁺ ions in the network crosslinking. It is hypothesised that this mechanism later transitions into a rearrangement of the ALE molecules, which eventually leads to a fibrous network structure with large voids.

生物膜EPS的特性取决于其成分与周围环境之间的多重相互作用。由于生物膜EPS的高度复杂性，其成分的表征还远远不够彻底，并且尚无法确定这些相互作用。因此，在这项工作中，我们使用细菌藻酸盐样胞外多糖（ALEs）的凝胶作为生物膜EPS的模型组件。已经检查了这些凝胶的内聚性能，它们是CaCl ₂和KCl浓度的函数。迄今为止，通过ALE溶液的死端过滤在膜上形成了ALE凝胶层。阳离子Ca ²⁺和K ^+的积累根据ALE中固定的负电荷，可以从Donnan平衡模型中很好地预测凝胶中的Cb含量。这表明Ca ²⁺与ALE没有特异性结合，并且在实验的时间尺度上，Ca ²⁺离子可以在凝胶和周围溶液中自由分布。根据Donnan平衡估计ALE中固定负电荷的浓度约为1 mmol / g VSS（挥发性悬浮固体，有机物质）。此外，预测到了H ⁺的积累。具有更多的CaCl凝胶₂在上清液更紧凑和孔比那些更高的渗透压用更少的CaCl ₂，揭示Ca的作用²⁺离子在网络中交联。假设该机制随后转变为ALE分子的重排，最终导致具有大空隙的纤维网络结构。