Long-term storage and reusability of living bacteriaencapsulated polyethylene oxide nanofiber mats for reactive dye removal

From food to environmental applications, the encapsulation of bio-objects in nanofibers is widely used. In particular, for improved and sustainable performance of bioremediation, the system requires the development of cost-effective nanomaterials that containing living microorganisms for textile wastewater treatment is required. Here, bacteria-encapsulated polyethylene oxide (PEO) nanofibers (Nfs) were prepared by electrospinning. According to the Scanning Electron Microscope (SEM) images, PEO-Nfs show bead-free morphology and homogeneous distribution, while random expansions are observed in the nanofibers after bacterial encapsulation. While the number of live bacteria in the polymer before electrospinning was 1010 CFU/mL, the number of live bacteria encapsulated after spinning was 108 CFU/mL. This proves that nanofibers carry a very high number of bacteria after electrospinning which is supported by Fluorescence microscope images. Furthermore, an ATR-FTIR study confirmed the molecular interactions between PEO and bacteria in the nanofibers. The removal efficiency of PEO_bacteria-Nfs was 26.6 ± 0.3% at 5 ppm and 9 ± 0.1% at 20 ppm dye concentration. Under storage conditions of +4 °C, the bacteria-encapsulated in PEO-Nfs show cell viability for more than 60 days. In order to extend the research on bacteria-encapsulated polymer Nfs, we explored the possibility of extending the life of bacteria in electrospun Nfs by crosslinking approaches using non-toxic calcium ions. The composite Nf mats were therefore reused for up to 4 repeated cycles.