School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China.
Hospital of Stomatology, Guanghua School of Stomatology, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou 510055, China.
Water Res. 2023 Sep 1;243:120339. doi: 10.1016/j.watres.2023.120339. Epub 2023 Jul 13.
Photosensitized biohybrid system (PBS) enables bacteria to exploit light energy harvested by semiconductors for rapid pollutants transformation, possessing a promising future for water reclamation. Maintaining a biocompatible environment under photocatalytic conditions is the key to developing PBS-based treatment technologies. Natural microbial cells are surrounded by extracellular polymeric substances (EPS) that either be tightly bound to the cell wall (i.e., tightly bound EPS, tbEPS) or loosely associated with cell surface (i.e., loosely bound EPS, lbEPS), which provide protection from unfavorable environment. We hypothesized that providing EPS fractions can enhance bacterial viability under adverse environment created by photocatalytic reactions. We constructed a model PBS consisting of Shewanella oneidensis and CdS using Cr(VI) as the target pollutant. Results showed complete removal of 25 mg/L Cr(VI) within 90 min without an electron donor, which may mainly rely on the synergistic effect of CdS and bacteria on photoelectron transfer. Long-term cycling experiment of pristine PBS and PBS with extra EPS fractions (including lbEPS and tbEPS) for Cr(VI) treatment showed that PBS with extra lbEPS achieved efficient Cr(VI) removal within five consecutive batch treatment cycles, compared to the three cycles both in pristine PBS and PBS with tbEPS. After addition of lbEPS, the accumulation of reactive oxygen species (ROS) was greatly reduced via the EPS-capping effect and quenching effect, and the toxic metal internalization potential was lowered by complexation with Cd and Cr, resulting in enhanced bacterial viability during photocatalysis. This facile and efficient cytoprotective method helps the rational design of PBS for environmental remediation.
光敏生物杂化系统 (PBS) 使细菌能够利用半导体收集的光能快速转化污染物，在水回用方面具有广阔的前景。在光催化条件下保持生物相容性环境是开发基于 PBS 的处理技术的关键。天然微生物细胞被细胞外聚合物物质 (EPS) 包围，这些物质要么紧密结合在细胞壁上（即紧密结合的 EPS，tbEPS），要么与细胞表面松散结合（即松散结合的 EPS，lbEPS），为细胞提供了免受不利环境的保护。我们假设提供 EPS 分数可以增强细菌在光催化反应产生的不利环境下的生存能力。我们使用 Cr(VI) 作为目标污染物，构建了由 Shewanella oneidensis 和 CdS 组成的模型 PBS。结果表明，在没有电子供体的情况下，25mg/L Cr(VI) 在 90min 内完全去除，这可能主要依赖于 CdS 和细菌对光电转移的协同作用。原始 PBS 和含有额外 EPS 分数（包括 lbEPS 和 tbEPS）的 PBS 进行 Cr(VI) 处理的长期循环实验表明，与原始 PBS 和含有 tbEPS 的 PBS 相比，含有额外 lbEPS 的 PBS 在连续五次批处理循环中实现了高效的 Cr(VI)去除。在添加 lbEPS 后，通过 EPS 封端效应和淬灭效应大大减少了活性氧物质 (ROS) 的积累，并且通过与 Cd 和 Cr 的络合降低了有毒金属的内化潜力，从而在光催化过程中提高了细菌的生存能力。这种简便有效的细胞保护方法有助于合理设计用于环境修复的 PBS。
