Saingam Prakit, Rasyid Rosita, Abrahamson Britt, Lie Thomas J, Godfrey Bruce J, Himmelfarb Jonathan, Winkler Mari K H
Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, United States.
Department of Microbiology, University of Washington, Seattle, WA, United States.
Front Microbiol. 2025 May 21;16:1577556. doi: 10.3389/fmicb.2025.1577556. eCollection 2025.
Individuals with chronic kidney disease (CKD) suffer from uremia, a condition characterized by the accumulation of uremic toxin in the blood. The aromatic uremic toxin p-cresol, a byproduct of tyrosine fermentation in the gut, binds to plasma albumin and cannot be removed with dialysis. However, the ingestion of densified p-cresol degrading microorganisms encapsulated in protective hydrogel beads could provide a therapeutic benefit by removing p-cresol from the colon. In this study the p-cresol degradation capacity of a known anaerobic, p-cresol degrading microorganism, S2, encapsulated in polyvinyl alcohol and sodium alginate (PVA/SA) hydrogels was evaluated as a potential oral delivery method for intestinal p-cresol removal. Planktonic degradation was induced through prior p-cresol exposure, yielding a 100% removal efficiency at a rate of 92 nmol (Log CFU) h when exposed to 1.2 mM of p-cresol at 37°C. Increasing p-cresol concentrations inhibited p-cresol degradation. Hydrogel encapsulation of the bacteria supported high cell density packaging at 2.5 Log CFU (mL hydrogel) and high activity right after hydrogel production, and more rapid activity than the planktonic cells, providing a powerful p-cresol-consuming microbial sink. Our experimental design mimicked distal colon conditions with an initial p-cresol level of 0.60 mM and at a pH 7 where the p-cresol degradation capacity of encapsulated culture was 2.3 × 10 nmol (Log CFU) h . The encapsulation of 10-fold increased cell concentrations resulted in more than 2-fold increased degradation rates. With the cell densification, the estimated daily hydrogel intake could be reduced from 134 mL to 58 mL to match daily exposure, thereby achieving mass balance. The effective removal rates were due to well distribution of bacteria cells within the hydrogels. The hydrogels with p-cresol pre-induced biomass showed immediate p-cresol removal even at p-cresol higher than 1.0 mM concentration. The current study demonstrated the potential application of encapsulated S2 for the removal of colon p-cresol hence offloading the kidney from processing protein-bound uremic toxins. Further research in hydrogel design could yield efficient removal as well as cell encapsulation.
慢性肾脏病（CKD）患者会出现尿毒症，其特征是血液中尿毒症毒素的积累。芳香族尿毒症毒素对甲酚是肠道中酪氨酸发酵的副产物，它与血浆白蛋白结合，无法通过透析清除。然而，摄入包裹在保护性水凝胶珠中的高密度对甲酚降解微生物，可能通过从结肠中清除对甲酚而带来治疗益处。在本研究中，评估了包裹在聚乙烯醇和海藻酸钠（PVA/SA）水凝胶中的已知厌氧对甲酚降解微生物S2的对甲酚降解能力，作为一种潜在的口服给药方法用于肠道对甲酚的清除。通过预先暴露于对甲酚诱导浮游降解，当在37°C下暴露于1.2 mM对甲酚时，去除效率达到100%，速率为92 nmol（Log CFU）/h。对甲酚浓度的增加会抑制对甲酚降解。细菌的水凝胶包封支持在2.5 Log CFU/（mL水凝胶）下的高细胞密度包装，并且在水凝胶生产后立即具有高活性，且比浮游细胞的活性更高，提供了一个强大的消耗对甲酚的微生物库。我们的实验设计模拟了远端结肠条件，初始对甲酚水平为0.60 mM，pH为7，在此条件下包封培养物的对甲酚降解能力为2.3×10 nmol（Log CFU）/h。细胞浓度增加10倍的包封导致降解速率增加超过2倍。随着细胞致密化，估计每日水凝胶摄入量可从134 mL减少到58 mL以匹配每日暴露量，从而实现质量平衡。有效的去除率归因于细菌细胞在水凝胶内的良好分布。含有对甲酚预诱导生物量的水凝胶即使在对甲酚浓度高于1.0 mM时也能立即去除对甲酚。当前研究证明了包封的S2在去除结肠对甲酚方面的潜在应用，从而减轻肾脏处理与蛋白质结合的尿毒症毒素的负担。在水凝胶设计方面的进一步研究可能会产生高效的去除以及细胞包封效果。
