LABORATORY-SCALE INVESTIGATIONS INTO THE USE OF EXTREMELY THERMOPHILIC PROTEINASES FOR CLEANING ULTRAFILTRATION MEMBRANES FOULED DURING WHEY PROCESSING

The potential of proteolytic enzymes from extremely thermophilic eubacteria to clear ultrafiltration membranes fouled during the processing of whey was investigated. The enzymes were initially tested for their ability to hydrolyse freeze-dried preparations of material removed from fouled ultrafiltration membranes. Under the conditions used, the serine proteinases from Thermus strains were more efficient than the metalloproteinase from Bacillus strain EA.1, and were subsequently investigated for their ability to clear fouled membrane discs using purpose-built laboratory scale equipment. The proteinase from Thermus strain Rt4.1A proved most effective and gave a linear increase of water flux with time when used to treat fouled membranes at 70-degrees-C. The rate of clearing and final flux levels obtained using enzyme alone were lower than those obtained using alkaline-EDTA. The performance of the enzyme was, however, synergistically enhanced using the anionic detergent sodium dodecyl sulphate in combination with the enzyme.