Quantitative analysis of membrane fouling by protein mixtures using MALDI-MS

• Published in: Biotechnology and bioengineering Vol. 85; no. 2; pp. 190 - 201
• Main Authors: Chan, R., Chen, Vicky, Bucknall, M. P.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 20.01.2004; Wiley
• Subjects: Biodeterioration. Biofouling; Biological and medical sciences; Biotechnology; Complex Mixtures - isolation & purification; critical flux; Equipment Failure Analysis - methods; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; Hydrophobic and Hydrophilic Interactions; Industrial applications and implications. Economical aspects; Lactoglobulins - isolation & purification; MALDI; mass spectrometry; Membranes, Artificial; protein fouling; Proteins - isolation & purification; quantification; Reproducibility of Results; Sensitivity and Specificity; Serum Albumin, Bovine - isolation & purification; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; ultrafiltration; Ultrafiltration - instrumentation; Ultrafiltration - methods; Fouling; Ultrafiltration; Biofouling; Membrane filtration; Matrix assisted laser desorption ionization; Mass spectrometry; Protein; Quantitative analysis
• ISSN: 0006-3592; 1097-0290
• DOI: 10.1002/bit.10866

Binary aqueous solutions of bovine serum albumin (BSA) and β‐lactoglobulin (bLG) were subject to flux‐stepping and constant flux ultrafiltration to identify the apparent critical flux and to study the mechanisms and factors affecting fouling when the membrane is permeable to one protein component. Membranes from these filtration experiments were analyzed using matrix‐assisted laser desorption ionization mass spectrometry (MALDI‐MS) to locate and quantify levels of fouling below and above the apparent critical flux. Hydrophilic (PLTK) regenerated cellulose and hydrophobic (PBTK) polysulfone asymmetric membranes were used, both of 30 kDa nominal molecular weight cut‐off. For the hydrophilic PLTK membrane, protein deposition was shown to depend on electrostatic forces, exhibiting little or no fouling when the proteins had the same charge sign as that of the membrane. This was found to apply for both dilute equal mass‐per‐unit‐volume and equimolar binary mixtures. For the PBTK membrane, hydrophobic protein‐membrane attractive forces were sufficiently strong to cause deposition of bLG even in the presence of repulsive electrostatic forces. For the PBTK membrane deposition exceeded monolayer coverage below and above apparent critical flux conditions but for the PLTK membrane this generally occurred when the apparent critical flux was exceeded. MALDI‐MS was shown to be a facile direct analytical technique for individually quantifying adsorbed proteins on membrane surfaces at levels as low as 50 fmol/mm2. The high levels of compound specificity inherent to mass spectrometry make this approach especially suited to the quantification of individual components in mixed deposits. In this study, MALDI‐MS was found to be successful in identifying and quantifying the protein species responsible for fouling. © 2003 Wiley Periodicals, Inc.