How do we stop biofilms forming?

Many techniques and chemicals have been tried in an attempt to stop biofilms developing. For aquatic biofilms in inland waters or at sea these include the use of air bubbles, manual cleaning, magnetism, thermal control, colour control, chlorination, coating the surface with a bio-toxin and creating a smooth surface. The most widely used technique for submerged man-made materials such as boats, ropes, pipes and structures, is to coat the surface with an anti-foulant (antifouling) paint. These paints can be toxic or resistant to attachment. The use of ultrasound has also been used for biofilm control on food contact surfaces, mainly in combination with chemical-based strategies.

The following sections will describe the most important methods to stop biofilms forming in different situations, including some novel strategies such as the use of bacteriophages, bacteriocins, quorum sensing inhibitors, essential oils, high hydrostatic pressure and non-thermal plasma.

Biocides
Biocide effectiveness on biofilms is thought to be approximately three orders of magnitude lower compared to bacterial suspensions. However, this might be misleading as biofilms vary in thickness and composition, so biocides might work better in some areas than others. Oxidative biocides are often used in industry in control of biofilms. They are proposed to […]
Antimicrobials
Antimicrobials work against biofilm-enclosed microorganisms by slowing them down; they delay their diffusion, scavenging or inactivate them as well as altering the local microenvironment of the cells, resulting in slower growth rate and stress adaptation. However, the glue-like matrix of biofilms (polysaccharides, proteins, lipids, and nucleic acids) makes antimicrobials less effective, as it forms a […]
Electrical charge
Research has shown that cells in biofilms use electrochemical signalling to communicate and cooperate with each other. Electrochemical biofilm control is a technology where surface properties or reactions are controlled to delay or prevent cell attachment or to remove existing cells from that surface. Generally, electrochemical biofilm control is applied to targeted surfaces that are […]
Photocatalysts
Diverse types of nanoparticles show photocatalytic properties, where the absorption of an specific wavelength is used for generating (accelerating) a chemical reaction, including destruction of microbial cells, generally due to reactive oxygen species (ROS) generation (Nica et al., 2017). In this sense, TiO2NPs, containing 1% Fe and N, structured as a thin layer on a […]
Non-thermal plasma
Non-thermal plasma is produced at atmospheric pressure by mixing UV light with oxygen, nitrogen, ozone, and water and helium, under an electrical discharge. It is able to destroy bacterial biofilms of Gram-negative (Pseudomonas, S. enterica) or Gram-positive (Bacillusspp.) species in just 10 min, However, its use is still restricted to some laboratory applications, due to its […]
High hydrostatic pressure
Use of pressure in food processing goes back to the time of Napoleon Bonaparte. It is originated in the bottled foods invented by Nicolas Appert at that time. Foods were hermetically sealed in a can and then heated. Vapour in the can raised the inner pressure to several atmospheres of pressure and the foods were […]
Non-stick coatings
The most common types of non-stick coatings used on cookware are; 1. Polytetrafluoroethylene (PTFE), a well-known brand of which is TeflonTM 2. Ceramic coatings 3. Silicon coatings 4. Super hydrophobic (water repelling) coatings 5. Enamelled cast iron coatings Other non-stick coatings include Anodised Aluminium and seasoned cast iron. Biofilms can still grow on non-stick coatings though…. […]
Essential oils
Plant-based essential oils are primarily a species specific complex mixture of monoterpenoids (such as borneol, camphor, carvacrol, eucalyptol, limonene, pinene, thujone), sesquiterpenoids (such as caryophyllene, humulene) and flavonoids (such as cinnamaldehyde and other phenolic acids). For example, a 24 h old aureusbiofilm on steel was reduced from 107 CFU/mL to 103 CFU/mL using a Cinnamomum cassia essential oil microemulsion (very […]
Quorum Sensing inhibition
Many small molecules can inhibit cGMP biosynthesis, such as the terpenoid saponin, nitric oxide generating compounds, azathioprine, or sRNAs. Based on this, an effective strategy for eradicating food-associated bacterial biofilms is to prevent their formation by using Quorum Sensing (QS) inhibition. Unlike bactericidal strategies, compounds targeting QS and biofilm formation cause less selection pressure and, […]
Bacteriocins
The use of bacteriocins in the food industry is useful to prevent biofilm formation on different surfaces. These antimicrobial agents can extend the expiration date of a given food as well, protects against alterations during refrigeration, lowers food spoilage, prevents the transmission of foodborne pathogens, diminishes chemical preservative concentrations and reduces the number of temperature […]
Biosurfactants
When surfaces used in the food industry are treated with lichenysin fewer microbes attach to them. For example, the number of MRSA microbes was halved at 8.3 μg/mL, as were the numbers of C. albicans (at 17.2 μg/mL), Y. enterocolitica (at 16.1 μg/mL) and C. jejuni (at 188.5 μg/mL) (Coronel-León et al., 2016). Fengycin, iturin, and surfactin are similar […]
Copper coatings
The mechanisms behind the antimicrobial properties of copper surfaces are related to the release of copper ions from metallic surfaces. They are only effective when there is direct contact between microbes and the copper surface and effectiveness varies amongst microbe species and on their state: free floating in liquid (planktonic), stuck on a surface, or […]
Enzymatic disruption
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 […]
Chemical treatments for biofilms
Chlorine-based sanitisers are the most widely used in the food industry, but resistance to chlorine treatments has arisen in some microbes. For example, in enterica, chlorine resistance was correlated to its cellulose production phenotype. This phenotype depended on the environmental stress conditions found in the food processing plants. Aqueous ClO2is the most widely used sanitiser […]
Antifouling coatings
Antifouling coatings are specialised paints applied to ships or underwater structures to slow marine growth. In addition to preventing marine growth, the coating can also act as a barrier against corrosion that would degrade and weaken the metal and improve the flow of water passing along the hull of vessels, maintaining their speed through the […]
Bacteriophages
Bacteriophages with their inate ability to target bacteria could be of interest for treating biofilms in the clinical setting. Bacteria growing in layers, or biofilms, are often highly resistant to antibiotics and are capable of surviving in very harsh environments. Treating biofilm-related infections is a major challenge for doctors today. Bacteriophages, or ‘phages’ for short […]
Nanoparticles
Nanoparticles with anti-biofilm activity have gained attention in the past decade as some can naturally kill bacteria (they are bactericidal) and a few also have biofilm-eradicating properties. The unique properties of nanoparticles (NPs) distinguish them from their bulk chemical counterparts. One such property is their large surface area to volume ratio, which creates a higher […]