Bacterially induced synthesis of struvite under seawater stress: Characteristics and application potential

Biological synthesis of struvite for phosphorus fixation represents an effective strategy to mitigate water eutrophication and recycle phosphorus from wastewater. However, its large-scale application remains restricted by the high cost of conventional magnesium salts and the inhibition of the complex wastewater environment on bacterial growth. In this study, Bacillus velezensis was employed to induce struvite mineralization under seawater stress. The mineralized products were characterized for phase composition, structure, and morphology using SEM-EDS, XRD, FT-IR, and BET, while the adsorption capability of the synthesized struvite toward Cd²⁺ was investigated. The results showed that under seawater stress, this strain secretes glycine-rich proteins that mitigate the detrimental effects of seawater, and it not only utilizes Mg²⁺ and inorganic phosphorus present in the seawater medium but also metabolizes organic phosphorus to induce the synthesis of struvite. Among them, the bacterially induced mineralization achieved a 98.30% removal of total phosphorus from the culture medium, with 55.06% of the initial total phosphorus being immobilized and recovered in the form of struvite. The biosynthesized struvite exhibited a specific surface area of 140.9718 m²/g, significantly higher than that of chemically synthesized struvite (79.4863 m²/g); and its maximum adsorption capacity for Cd²⁺ reached 386.10 mg/g, markedly exceeding that of the chemically synthesized product (212.92 mg/g). Furthermore, the mechanism of bacterially induced struvite mineralization under seawater stress was clarified. This study presents a novel idea for the cost-effective biosynthesis of struvite and ecological treatment of eutrophication in coastal waters.