Biodegradation of phenol by entrapped cell of Debaryomyces sp. with nano-Fe3O4 under hypersaline conditions

•The fungal strain Debaryomyces sp. was entrapped into Ca-alginate beads.•Immobilized cells could tolerate harsher conditions compared with free cells.•The addition of nano-Fe3O4 in alginate beads notably improved phenol biodegradation.•Immobilized strain could be used repeatedly for phenol removal in saline conditions.

Phenol-containing industrial wastewater disposal has received much attention in recent years due to its toxicity and slow biodegradation. In this work, the isolated fungal strain Debaryomyces sp. was entrapped into Ca-alginate beads with nanoscale Fe3O4 to improve phenol biodegradation ability. Freely suspended cells as well as Ca-alginate immobilized cells without nanoscale particles were also prepared. Phenol removal by free cells and two kinds of Ca-alginate beads was evaluated with different initial phenol concentrations, temperatures, and salinities. The phenol biodegradation kinetics and optimal dosage of nano-Fe3O4 during the preparation of Ca-alginate beads were also determined. The results showed that immobilized Debaryomyces strain had better biodegradation performance than free cells under harsh conditions. Phenol removal rates were highest when using magnetically immobilized cells, followed by nonmagnetically cells. More than 99.9% of phenol was degraded within 80 h by immobilized cells with nano-Fe3O4 when initial phenol concentration was over 900 mg L−1 while the phenol removal efficiencies of free cell and immobilized cells without nano-Fe3O4 were 34.5% and 81.3%, respectively during the same periods of time. The reusability tests were carried out and the results indicated good stability of immobilized cells in saline environments, which was practical in actual industrial wastewater treatment.