Xanthan gum as a carrier for bacterial cell entrapment: Developing a novel immobilised biocatalyst

Xanthan gum (XAN) is a widely used polysaccharide in various industries. Because of its unique properties, in this study, an attempt was made to adopt the procedure of xanthan gum cross-linking for the entrapment of bacterial cells that are able to biodegrade naproxen. The developed procedure proved to be completely neutral for Bacillus thuringiensis B1(2015b) cells, which demonstrated a survival rate of 99%. A negative impact of entrapment was noted for strain Planococcus sp. S5, which showed a survival rate in the 93–51% range. To achieve good mechanical properties of the composites, they were additionally hardened using polydopamine (PDA). XAN/PDA composites revealed a high stability in a wide range of pH, and their sorption capacity included both cationic and anionic molecules. Analysis of the survival rate during storage at 4 °C in 0.9% NaCl showed that, after 35 days, 98–99% of B1(2015b) and 47% of S5 cells entrapped in XAN/PDA remained alive. This study also presents the results of naproxen biodegradation conducted using XAN/PDA/B1(2015b) in a trickling filter with autochthonous microflora. Hence, owing to the significant acceleration of drug biodegradation (1 mg/L in 14 days) and the chemical oxygen demand removal, the entrapped B1(2015b) cells in XAN/PDA composites showed a promising potential in bioremediation studies and industrial applications.