Cytoprotective alginate microcapsule serves as a shield for microalgal encapsulation defensing sulfamethoxazole threats and safeguarding nutrient recovery

Microalgal encapsulation technology is expected to broaden more possibilities for employing microalgae for upgrading conventional biological wastewater treatment. However, only limited and fragmented information is currently available on microalgal encapsulation and pollutant removal. It is ambiguous whether it hold potential for wastewater treatment. Particularly, it remains to be determined whether this technology can provide more possibilities in harsh sewage environments. Here, potential of encapsulated technology to recover nutrients from wastewater was examined, simultaneously compared with a commonly adopted suspended system. Results indicate the encapsulated microalgal system showed outstanding advantages in nutrient recovery and defense against antibiotic threats. Moreover, by examining the cellular oxidative stress response and changes of the photosynthetic system, the encapsulated system exhibited potential cytoprotective advantages to microalgal cells for defensing antibiotic threats. Molecular dynamics simulation revealed that the differences among superficial aggregation between the nutrients’ ions and molecular sulfamethoxazole on the cross-linked alginate microcapsule surface dominated the nutrient recovery and cytoprotective functions. Ultimately, the molecular nature of pollutants was found to be the most critical aspect for predicting the application of this microalgal microcapsule. Cytoprotective systems created with alginate microcapsules can potentially handle more diverse threats with a single type of surface charge in their outermost layer. This work explores the potential of microalgal encapsulation for protecting cells against environmental stress (sulfamethoxazole threats) while treating wastewater. It was hypothesized that higher-population density within the microenvironment can provide benefits of cellular aggregation and collaboration, and the encapsulated medium can withstand or provide a buffering zone against instantaneous or severe external threats. Potential for nutrient recovery from effluent was examined, and it was found that microalgal cells within the system presented with better physiological status. Further, the cytoprotective mechanism of the alginate microcapsule was decoded through cellular physiological status evaluation and computational simulation.