Postlethwaite, Jonathan; (2004) Vibrating membrane filtration : Microfiltration performance during the processing of biological feedstreams. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Conventional crossflow microfiltration systems rely on high liquid velocities to generate shear at the liquid-membrane interface. Shear is necessary in order to maintain acceptable flux and product transmission levels especially when processing fluids with a high solids loading. PallSep is a new technology that uses mechanical energy generated by vibration to create high intermittent shear rates at the membrane surface thus decoupling shear and liquid crossflow velocity. High permeate fluxes can then be maintained over extended periods of operation at low retentate flow-rates. This work considers the use of a PallSep PS10 (0.2 m2 membrane area) for the recovery of both proteins and low molecular weight molecules from complex biological feedstreams. For the optimisation of protein recovery it is necessary to understand how flux and transmission levels vary as a function of membrane operation. In this work, a model system of baker's yeast (Saccharomyces cerevisae) and BSA is used to study the effect of membrane operation on permeate flux and protein transmission. Similarly, the recovery of polyketide antibiotics from whole fermentation broths is a particularly challenging application for membrane technologies. Such broths typically have both a high viscosity and solids loading and the economics of the process require >95 % w/w product recovery with a minimum of diafiltration. In this work the interactions between fermentation and microfiltration operations are investigated, examining the recovery of the polyketide antibiotic erythromycin from Saccharopolyspora erythraea fermentation broths. The results for both systems indicate that flux and transmission levels are independent of liquid crossflow velocity but critically dependant on membrane head amplitude and hence shear rate, membrane spacing, transmembrane pressure and the solids concentration of the process stream. The study has shown PallSep technology to be a viable alternative to conventional filtration technology for the processing of feed streams particularly those with a viscous nature or containing high levels of suspended solids.

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