Purification of cellulase fermentation broth via low cost ceramic microfiltration membranes with nanofibers-like attapulgite separation layers

This paper reports the study of low cost ceramic microfiltration membranes with a separation layer of attapulgite nanofibers (attapulgite microfiltration membrane), used to clarify the cellulase fermentation fluid in order to enhance the quality of cellulase products. Based on resistance-in series model, the influence of membrane microstructure and operating conditions on the decline in membrane flux was investigated. The appropriate method for cleaning membranes that had undergone fouling was also found. The results show that an attapulgite microfiltration membrane with mean pore size of 0.12 μm is suitable for treating a cellulase fermentation fluid. The appropriate operating conditions were found to be the following: T = 30 ± 3 °C, ΔP = 0.10 MPa, and v = 4 m/s. The dominant component of the total resistance (Rt) was the reversible fouling resistance (Rrev), whereas the irreversible fouling resistance (Rirr) was less important. In conditions of low trans-membrane pressure and high velocity, the fouled attapulgite microfiltration membrane could be satisfactorily regenerated using water rinsing and chemical cleaning. The results obtained in this work indicated that attapulgite microfiltration membrane separation may represent a feasible pretreatment for cellulase fermentation broth. The resistance-in-series analysis may provide additional insight into the relative importance of different fouling mechanisms.