title: Resistance of the constitutive microflora of biofilms formed on whey reverse-osmosis membranes to individual cleaning steps of a typical clean-in-place protocol.
abstract: This experiment evaluates the effectiveness of individual steps of a clean-in-place protocol against the biofilm constitutive microflora isolated from the biofilms developed on whey reverse-osmosis membranes, aged 2 to 14 mo, under industrial processing conditions. The isolates used for the in vitro resistance studies included species of Bacillus, Enterococcus, Streptococcus, Staphylococcus, Micrococcus, Aeromonas, Corynebacterium, Pseudomonas, Klebsiella, and Escherichia. The 6 cleaning steps (alkali, surfactant, acid, enzyme, a second surfactant, and sanitizer treatment) revealed resistance of isolates in both planktonic and biofilm-embedded cell states. The most effective step was the acid treatment, which resulted in 4.54 to 7.90 and 2.09 to 5.02 log reductions of the planktonic and biofilm-embedded cells, respectively. Although the sanitizer step causing a reduction of 4.91 to 8.33 log in the case of planktonic cells, it was less effective against the biofilm-embedded cells, resulting in a reduction of 0.59 to 1.64 log. Bacillus spp. showed the highest resistance in both planktonic, as well as embedded cell states.
authors: Midwest Dairy Foods Research Center, Dairy Science Department, South Dakota State University, Brookings 57006. Electronic address: Sanjeev.anand@sdstate.edu.
authors: Sanjeev
authors: S
authors: Anand
authors: Diwakar
authors: D
authors: Singh
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects* / Q000302:isolation & purification; D018441:Biofilms / Q000187:drug effects*; D003611:Dairy Products / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D005516:Food Microbiology / Q000379:methods*; D064307:Microbiota / Q000187:drug effects* / Q000502:physiology; D009995:Osmosis; D013242:Sterilization / Q000379:methods*
keywords: biofilm; cleaning; membrane; reverse osmosis