Kill two birds with one stone: Biochar immobilised polydopamine coated compound bacterial agent for remediation of dibutyl phthalate contaminated soil.

The severe contamination of the plasticiser dibutyl phthalate (DBP) in agriculture soils is often accompanied by a decrease in nutrient utilisation. Though the combined application of a variety of microorganisms can simultaneously address the problems of soil contamination and nutrient deprivation, the activity and function of microorganisms can be severely inhibited by DBP, and studies on their protection under DBP contamination are almost non-existent. In this study, a compound bacterial agent KPSB was prepared by optimising with FeO-modified biochar loaded with DBP-degrading bacterium Enterobacterium sp. DNB-S2 and polydopamine (PDA)-coated potassium-solubilizing bacterium Paenibacillus sp. KT. The results showed that KPSB was able to simultaneously remove DBP and increase the soil available potassium (K) content. PDA has good biocompatibility and shielding effect, and the strain KT coated by it has more complete cell membrane and stronger ability to secrete low molecular weight organic acids to promote K solubilisation. The FeO-modified biochar with suitable pore structure, large specific surface area and abundant functional groups could provide a good growth microenvironment for functional microorganisms and support the growth of strains while promoting the degradation of DBP. The expression of DBP-degradation-related genes was significantly increased in KPSB, which promoted the removal of DBP. In addition, KPSB has good acid and alkali resistance and a wide range of temperature adaptability, and is able to remove DBP and increase the available K content better under different environmental conditions. These results will provide new perspectives for the research of in situ soil remediation technology.