Microbial fabrication of cellulose nanofiber-based ultrafiltration membrane: a sustainable strategy for membrane manufacture

Developing a sustainable separation membrane is imperative due to the growing environmental pollution caused by petrochemical-based polymers. Cellulose-based materials, including bacterial cellulose (BC), have exhibited potential as separation materials. Here, a novel BC membrane (BCM) is in-situ fabricated via microbial fermentation and physical post-treatment. Owing to the randomly assembled BC nanofibers and abundant hydroxyls on their surface, the obtained BCMs possess three-dimensional network structure with strong hydrophilicity. The BCMs properties can be manipulated by adjusting fermentation and drying conditions, satisfying different purposes for practical use. Extending fermentation time from 3 to 10 days, bacteria secret more BC nanofibers and form a denser membrane structure. Freeze-dried BCMs have the most porous structure and exhibit the highest flux (up to 52 L m −2 h −1 ) and molecular weight cut-off (up to 1000 KDa) under 2 bar. Press-dried BCMs obtain the highest tensile strength (up to 241.16 MPa) and BSA retention (up to 94.44%). Heat-dried BCMs show good prospects in the pressure-driven membrane process considering flux and retention and demonstrate favorable stability and flux recovery ratios (85.51%~96.43%). Modification of BCMs by carboxymethyl cellulose further promotes membrane hydrophilicity but causes denser structures than original BCMs. The present study proposes a sustainable cellulose membrane manufacturing strategy and demonstrates BCMs can be favorable alternatives to petrochemical-based membranes.