Purification performance and mechanism of phenanthrene in water by beads-in-string structural laccase-carrying electrospun fibrous membranes

The beads-in-string structural laccase-carrying electrospun fibrous membranes (LCEFMs) were prepared by emulsion electrospinning technology, and the laccase could be successfully encapsulated in the beads of electrospun fibers in situ. Compared with the linear LCEFMs, the laccase load of the beads-in-string structural LCEFMs was doubled, and the retained laccase activity reached 78.9%. Furthermore, the storage and operational stability of the beads-in-string structural LCEFMs were significantly increased after glutaraldehyde cross-linking. The optimized LCEFMs were used for the purification of typical polycyclic aromatic hydrocarbons in water. The result showed that compared with free laccase, the degradation and removal efficiencies of phenanthrene by the beads-in-string structural LCEFMs were obviously enhanced. For phenanthrene solution with concentration from 0.01 to 2.00 mg/L, the adsorption and degradation efficiency of the beads-in-string structural LCEFMs could reach over 80% and 72%, respectively. Furthermore, the tolerance of LCEFMs to the changes in environmental factors such as pH, temperature was also dramatically improved, which was attributed to the concentrated immobilization of laccase in the bead and the protective effect of the fibrous shell on laccase. In addition, the toxicity of the luminescent bacteria was detected for evaluating the toxicity of phenanthrene solution. The results showed that the toxicity of phenanthrene solution was reduced after treated by free laccase or the beads-in-string structural LCEFMs. By contrast, the beads-in-string structural LCEFMs could reduce more toxicity of phenanthrene solution with different concentrations than free laccase.