The efficacy of different cleaners and sanitisers in cleaning biofilms on UF membranes used in the dairy industry

The efficacy of different cleaners and sanitisers for removing or killing Klebsiella oxytoca in biofilms on ultrafiltration (UF) membranes from the dairy industry was investigated. K. oxytoca B006 was grown individually and combined with another K. oxytoca strain, TR002, on polyethersulfone (PES) UF membranes in 5% whey medium in CBR 90 biofilm reactors. Both strains were previously isolated from New Zealand dairy plants. Three enzymatic cleaners were compared with sodium hypochlorite (pH 10.8–11) at 200 ppm free available chlorine (FAC) commonly used for cleaning-in-place (CIP) of UF membranes in the dairy industry. In addition, 4 sanitisers were used to treat the membranes after a CIP wash regime. The efficacy in reducing culturable bacteria in biofilms was measured using pour plate counting on standard plate count agar. QuatroZyme®, which is composed of mixed enzymes, performed slightly better than the other cleaners. The treatments with all the sanitisers improved cleaning. MIOX® EW anolyte (pH 6.8) (120 ppm) was the most effective sanitiser compared to the control CIP. However, PES UF membranes are known to be sensitive to oxidants at low pH and therefore the damage to these membranes by MIOX® EW anolyte needs to be determined.