Factors affecting the attachment of micro-organisms isolated from ultrafiltration and reverse osmosis membranes in dairy processing plants

To identify the types of micro-organisms involved in the formation of biofilms on dairy ultrafiltration and reverse osmosis membranes and investigate factors affecting the attachment of those isolates. Micro-organisms isolated from industrial membranes following standard cleaning were identified using the API culture identification system. Thirteen different isolates representing eight genera were isolated and their ability to attach to surfaces was compared using a microtitre plate assay. Three Klebsiella strains attached best, while mixed strains of Pseudomonas and Klebsiella attached better than individual strains. Whey enhanced the attachment of the isolates. The micro-organisms were characterized according to cell surface hydrophobicity using the microbial adhesion to hydrocarbon (MATH) test, and cell surface charge by measuring the zeta potential. These cell surface characteristics did not show a clear relationship with the attachment of our strains. A variety of different micro-organisms is associated with dairy ultrafiltration and reverse osmosis membranes after cleaning, suggesting several possible sources of contamination. The cleaning of these membranes may be inadequate. The attachment of the different isolates is highly variable and enhanced in the presence of whey. Knowledge of persistent microflora colonizing dairy membrane systems will help develop strategies to mitigate biofilm development in this environment, improving hygiene in membrane processing plants.