The major structural components of biofilms are mainly proteins and polysaccharides (complex sugars). Therefore, enzymes that break these substances down, like proteases (e.g., serine proteases, proteinase K, pepsin and trypsin) and glycosidases (e.g., amylases, dextranase and pectinase) are always the first option for biofilm removal. Pectin methylesterase, for example, is an enzyme capable of reducing biofilm formation in bioreactors. This is extremely important to the food industry as it can be used as a pre-treatment for various machines and pipes.
Other enzymes such as amylases, cellulases, lyases, glycosidases (e.g. dispersin B) and DNAses, are present in the industrial detergents commonly used in the food industry to remove biofilms. For example, a treatment with several cellulases, followed by immersion in a bath of cetyltrimethyl ammonium bromide, completely removed a biofilm made up of seven enterica strains known to be present on meat processing surfaces. Alpha-amylase is another enzyme that can effectively degrade Streptococcus aureus biofilms.
Proteases generally have lower specificity and so are more efficient in treating a wide range of different biofilms. Once the biofilm matrix has been partly degraded by proteases, it can be completely removed by mechanical treatments and it is more sensitive to sanitizers. For example, a mix of protease and trypsin combined with ultrasonic waves for 10 s was able to remove 96% of Escherichia coli biofilms on stainless steel surfaces in a dairy plant. Protease was also able to efficiently remove S. aureus biofilms on polystyrene surfaces. However, removal of other species in biofilms, such as P. aeruginosa, required mixtures of protease, amylase and cellulase. Subtilisins are serine proteases and widely used in industry to combat biofilm formation by P. aeruginosa and Listeria monocytogenes. Serine proteases are produced by Bacillus spp. and degrade adhesins, which are the proteins that bacteria use to stick to surfaces and begin the process of biofilm development. Some new enzyme variants are even able to destroy biofilm components at 90°C, which enhances their industrial use as ingredients in detergents.
Some pathogens, such as Escherichia coli, Listeria monocytogenes and Streptococcus aureus also secrete DNA during biofilm formation. In these cases, enzymes that specifically degrade DNA (DNase) can be very effective.
The combination of enzymes with different activities, alongside other chemical (sanitisers) or physical (ultrasound) treatments enhanced removal of biofilms comprised of species like or Bacillus spp. However, implementing enzymes at an industrial scale is still hampered by the high cost of these treatments, mainly due to patent protections.
Further reading on enzymic disruption
Galié Serena, García-Gutiérrez Coral, Miguélez Elisa M., Villar Claudio J., Lombó Felipe. Biofilms in the Food Industry: Health Aspects and Control Methods. Frontiers in Microbiology, Volume 9, page 898, 2018. https://doi.org/10.3389/fmicb.2018.00898.
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