Removal of Microbial Biofilms from Dispense Equipment: The Effect of Enzymatic Pre-digestion and Detergent Treatment
2007
Walker, S.L. | Fourgialakis, M. | Cerezo, B. | Livens, S.
Microbial biofilms can form in dispense outlets as a result of poor or inadequate cleaning and can be difficult to remove using conventional practices. Enzymatic cleaners might help to remove biofilms by degrading the exopolysaccharide layers in which the microbes are embedded. A multispecies biofilm comprising wild type dispense isolates of Flavimonas oryzihabitans, Lactobacillus brevis, Leuconostoc mesenteroides and Saccharomyces cerevisiae was generated on a section of tubing and fitted into a pilot dispense system, which was left uncleaned for 12 weeks. After cleaning approximately 104 viable aerobes and 103 viable anaerobes were still present. Stainless steel coupons and pieces of dispense line contaminated with biofilm were incubated in the laboratory with an enzyme mix containing varying proportions of a-amylase, ss -glucuronidase, glucose oxidase, dextranase, protease and pectinase. Cultures grown on stainless steel had significantly (F pr. < 0.05) less viable cells than nonenzyme treated biofilms, but this was dependent on the microbial species. Typically Lactobacillus brevis was most susceptible to the enzyme treatment. Cultures grown on dispense line were much more resistant to enzymatic digestion. Pre-digestion with protease was most effective for removal of Lactobacillus brevis and Leuconostoc mesenteroides but not for Saccharomyces cerevisiae and Flavimonas oryzihabitans. In the simulated bar, predigestion with protease reduced the viable cell count by 0.64 log units for the aerobes and 1.9 log units for the anaerobes. This study demonstrates that pre-digestion with enzyme solutions before line cleaning is useful for treating heavily contaminated lines in trade.
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