Clarification Of Cellulase Fermentation Broth By Attapulgite Microfiltration Membrane

Cellulase is a general term for cellulolytic enzymes, which can degrade cellulose into reducing sugar, and play a vital role in the utilization of biomass energy. Nowadays, traditional clarification methods for cellulase fermentation broth include filtration plate, flocculation, centrifugation and so on. Their intrinsic disadvantages are low efficiency and low product quality. Membrane separation as a new separation technology has received great attention due to its low energy consumption and environment friendly. In this work, a type of new attapulgite ceramic membranes were prepared and used in cellulase fermentation broth sterilization process. The research contents included three aspects:clarification of cellulase fermentation broth by attapulgite membrane, fouling analysis and membrane regeneration, preparation of muti-channels attapulgite membrane and application in clarification cellulase fermentation broth.Attapulgite membrane is a new ceramic microfiltration membrane with a separation layer of attapulgite nanofibers. In this chapter, attapulgite membranes were used to clarify cellulase fermentation broth instead of conventional plate and frame filter press. The influences of membrane bore diameter and operating condition on treatment effects were investigated. The results show that attapulgite membrane with mean pore size of 0.12 um was suitable for treating cellulase fermentation broth at T= 30±3℃,△P=0.1 MPa, v=4 m·s-1. At this condition, turbudity of clarified cellulase fermentation broth was less than 1 NTU. The protein rejection rate was highest and cellulase activity lost lowest. Compared to filtration plate and 0.2 μm GrO2 ceramic membrane, the using of attapulgite membranes improved the quality of filtrate and reduced treatment cost.Membrane fouling is a bottleneck problem in the membrane proces. Based on resistance-in-series model, the influence of operating condition on resistance and different cleaning methods were investigated. The results show that the dominant component of the total resistance (Rt) was the reversible fouling resistance (Rrev), whereas the irreversible fouling resistance (Rirr) was less important. Under low trans-membrane pressure and high velocity, the fouled attapulgite membrane could be satisfactorily regenerated. The pure water flux can recover to 90% of the pristine one using water rinsing and chemical cleaning.In the end, multi-channels attapulgite membranes were prepared and applied to clarify cellulase fermentation broth in order to further study the technology feasibility. The influence of dipping time on membrane thickness, surface morphology, permeability and separating ability in cellulase fermentation were studied. The results show that the longer dipping time would increase the membrane thickness and the fiber layer accumulation density, thereby decreasing the pure water flux and increasing the flux in microfiltration cellulase fermentation broth due to the decreasing of pore blocking resistance (Rif).