Membrane fouling by cell-protein mixtures: in situ characterisation using multi-photon microscopy
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Published on: October 9, 2014
David J Hughes1, Zhanfeng Cui, Robert W Field
1Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK.
Abstract:
Fouling of the membrane by cell and protein mixtures can result in severe flux declines, leading to the eventual need to clean or replace the membrane. In this study multi-photon microscopy, a fluorescence-based technique is used to 3-D image in situ the fouling of microfiltration membranes by suspensions containing combinations of washed yeast, bovine serum albumin (BSA) and ovalbumin. Appropriate fluorescent labelling allows the three foulant species to be clearly identified. Images correlate well with filtration data and clearly show the cake of yeast cells capturing protein aggregates. The proteins exhibited very different filtration behaviour. When filtering washed yeast together with ovalbumin and/or a 50:50 mixture by mass of BSA and ovalbumin, the ovalbumin fouling dominates the system. Capture of aggregates by the cake did not reduce fouling of the membrane by the protein and increased the resistance of the cake. For mixtures of BSA and washed yeast, the presence of a cake of yeast cells did reduce fouling of the membrane by the protein, however, the extra resistance due to the cake resulted in a flux lower than that when filtering BSA alone.
Insights
Membrane fouling by yeast and proteins like ovalbumin significantly reduces filtration efficiency. Multi-photon microscopy visualized how yeast cakes capture proteins, impacting membrane performance and requiring further study for optimization.
Area of Science:
- Membrane science and technology
- Bioprocess engineering
- Materials science
Background:
- Membrane fouling by cell and protein mixtures causes significant flux decline.
- This necessitates frequent membrane cleaning or replacement, impacting process economics.
- Understanding fouling mechanisms is crucial for improving membrane longevity and performance.
Purpose of the Study:
- To investigate the in situ fouling mechanisms of microfiltration membranes using mixtures of yeast, bovine serum albumin (BSA), and ovalbumin.
- To correlate 3-D imaging data with filtration performance metrics.
- To elucidate the distinct fouling behaviors of different protein foulants in the presence of yeast cells.
Main Methods:
- Utilized multi-photon microscopy, a fluorescence-based imaging technique, for 3-D visualization of membrane fouling.
- Employed fluorescent labeling to differentiate between yeast cells, BSA, and ovalbumin.
- Collected filtration data alongside microscopic imaging to analyze flux decline and cake resistance.
Main Results:
- Multi-photon microscopy successfully visualized yeast cell cakes capturing protein aggregates.
- Ovalbumin fouling dominated systems containing yeast and ovalbumin (or BSA/ovalbumin mixtures), increasing cake resistance.
- Yeast cakes reduced BSA fouling but increased overall cake resistance, leading to lower flux than BSA alone.
Conclusions:
- The study highlights the differential fouling behavior of BSA and ovalbumin in the presence of yeast cells.
- Yeast cell cakes can exacerbate fouling by certain proteins while mitigating it for others.
- Findings provide insights into complex fouling scenarios, aiding in the development of strategies to manage membrane performance.
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