Biocatalytic nanocomposite polymeric membranes with bio-graphene for the sustainable mitigation of biofouling

Βiofilm-associated biofouling is a significant barrier to the proper functioning of the wastewater ultrafiltration membranes. Developing nanocomposite polymeric membranes that incorporate various enzymes offers a sustainable approach to water purification, increasing the lifespan of the membrane. In this study, bio-graphene (bG) was prepared through liquid graphite exfoliation in the presence of chitosan, thereby enriching the final material's antimicrobial properties. Three types of polyethersulfone (PES) membranes were prepared: unmodified PES, PES containing different concentrations of bG, and PES incorporating bG together with α-amylase and lysozyme. Their antimicrobial activity was then evaluated. Next, the biocatalytic characterization of the optimized membranes was conducted. The reusability of the two enzymes incorporated into the nanocomposite membranes was tested: the activity of α-amylase remained relatively high until the 8th cycle (∼42 %), while that of lysozyme was nearly depleted. Furthermore, the storage stability of the biocatalytic membranes was investigated, revealing that they retained more than 60 % of their catalytic activity and maintained good antibacterial activity. Next, the morphology of bG and nanocomposite polymeric membranes was further characterized with several spectroscopic and microscopic techniques. Finally, it was shown that the nanocomposite membranes exhibited higher anti-biofouling and antimicrobial performance than the unmodified PES membrane, ensuring stable performance in challenging wastewater environments.