This research was supported by the Consortium de Recherche et Innovations en Bioproc&#233;d&#233;s Industriels au Qu&#233;bec (CRIBIQ)(2016-049-C22), Agropur, Groupe Sani Marc, and the Natural Sciences and Engineering Research Council of Canada (NSERC) (RDCPJ516460-17). We thank Teresa Paniconi for the critical review of the manuscript.

The work contained in this article requires a biosafety level 2 laboratory and was previously approved (Project number 119689) by the Universit&#233; Laval institutional biosafety committee.
NOTE: The flowchart in Figure 1 represents a summary of the methodology combining static and dynamic approaches that was used to evaluate the efficacy of organic peroxyacids for eradicating biofilms.
1. Preparation of materials
<o...

<ol>
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K., McGuire, J., Daeschel, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+adhesion+and+detachment+of+bacteria+and+spores+on+food-contact+surfaces.">The adhesion and detachment of bacteria and spores on food-contact surfaces.</a> Trends in Food Science &amp; Technology. 7 (5), 152-157 (1996).</li><li>Gupta, S., Anand, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+pitting+corrosion+on+stainless+steel+(grades+304+and+316)+used+in+dairy+industry+by+biofilms+of+common+sporeformers.">Induction of pitting corrosion on stainless steel (grades 304 and 316) used in dairy industry by biofilms of common sporeformers.</a> International Journal of Dairy Technology. 71 (2), 519-531 (2018).</li><li>Marchand, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilm+formation+in+milk+production+and+processing+environments;+Influence+on+milk+quality+and+safety.">Biofilm formation in milk production and processing environments; Influence on milk quality and safety.</a> Comprehensive Reviews in Food Science and Food Safety. 11 (2), 133-147 (2012).</li><li>Silva, H. 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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resistance+to+benzalkonium+chloride,+peracetic+acid+and+nisin+during+formation+of+mature+biofilms+by+Listeria+monocytogenes.">Resistance to benzalkonium chloride, peracetic acid and nisin during formation of mature biofilms by Listeria monocytogenes.</a> Food Microbiology. 28 (3), 418-425 (2011).</li><li>Goetz, C., Larouche, J., Velez Aristizabal, M., Niboucha, N., Jean, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficacy+of+organic+peroxyacids+for+eliminating+biofilm+preformed+by+microorganisms+isolated+from+dairy+processing+plants.">Efficacy of organic peroxyacids for eliminating biofilm preformed by microorganisms isolated from dairy processing plants.</a> Applied and Environmental Microbiology. 88 (4), 0188921 (2022).</li><li>Vimont, A., Fliss, I., Jean, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+the+virucidal+potential+of+organic+peroxyacids+against+norovirus+on+food-contact+surfaces.">Study of the virucidal potential of organic peroxyacids against norovirus on food-contact surfaces.</a> Food and Environmental Virology. 7 (1), 49-57 (2015).</li><li>ASTM E2562-17. Standard Test Method for Quantification of Pseudomonas aeruginosa Biofilm Grown with High Shear and Continuous Flow using CDC Biofilm Reactor. ASTM International Available from: <a target="_blank" href="https://www.astm.org/e2562-17.html">https://www.astm.org/e2562-17.html</a> (2017)</li><li>ASTM E2871-19. Standard Test Method for Evaluating Disinfectant Efficacy Against Pseudomonas aeruginosa Biofilm Grown in CDC Biofilm Reactor Using Single Tube Method. ASTM International Available from: <a target="_blank" href="https://www.astm.org/e2871-19.html">https://www.astm.org/e2871-19.html</a> (2019)</li><li>Niboucha, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+different+sampling+methods+of+biofilm+formed+on+stainless-steel+surfaces+in+a+CDC+biofilm+reactor.">Comparative study of different sampling methods of biofilm formed on stainless-steel surfaces in a CDC biofilm reactor.</a> Frontiers in Microbiology. 13, 892181 (2022).</li><li>ASTM E2799-17. Standard Test Method for Testing Disinfectant Efficacy against Pseudomonas aeruginosa Biofilm using the MBEC Assay. ASTM International Available from: <a target="_blank" href="https://www.astm.org/e2799-17.html">https://www.astm.org/e2799-17.html</a> (2022)</li><li>Parker, A. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruggedness+and+reproducibility+of+the+MBEC+biofilm+disinfectant+efficacy+test.">Ruggedness and reproducibility of the MBEC biofilm disinfectant efficacy test.</a> Journal of Microbiological Methods. 102, 55-64 (2014).</li><li>Stewart, P. S., Parker, A. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+antimicrobial+efficacy+against+biofilms:+A+meta-analysis.">Measuring antimicrobial efficacy against biofilms: A meta-analysis.</a> Antimicrobial Agents and Chemotherapy. 63 (5), 00020 (2019).</li><li>Lindsay, D. K., Fouhy, K., Loh, M., Malakar, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+CDC+biofilm+bioreactor+is+a+suitable+method+to+grow+biofilms,+and+test+their+sanitiser+susceptibilities,+in+the+dairy+context.">The CDC biofilm bioreactor is a suitable method to grow biofilms, and test their sanitiser susceptibilities, in the dairy context.</a> International Dairy Journal. 126, 105264 (2022).</li><li>Buckingham-Meyer, K., Goeres, D. M., Hamilton, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+evaluation+of+biofilm+disinfectant+efficacy+tests.">Comparative evaluation of biofilm disinfectant efficacy tests.</a> Journal of Microbiological Methods. 70 (2), 236-244 (2007).</li><li>Goeres, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+assessment+of+a+laboratory+method+for+growing+biofilms.">Statistical assessment of a laboratory method for growing biofilms.</a> Microbiology (Reading). 151, 757-762 (2005).</li><li>Williams, D. L., Woodbury, K. L., Haymond, B. S., Parker, A. E., Bloebaum, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+CDC+biofilm+reactor+to+produce+mature+biofilms+on+the+surface+of+peek+membranes+for+an+in+vivo+animal+model+application.">A modified CDC biofilm reactor to produce mature biofilms on the surface of peek membranes for an in vivo animal model application.</a> Current Microbiology. 62 (6), 1657-1663 (2011).</li><li>Pieranski, M. 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B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biofilm+formation+during+hexadecane+degradation+and+the+effects+of+flow+field+and+shear+stresses.">Biofilm formation during hexadecane degradation and the effects of flow field and shear stresses.</a> Annual Transactions - The Nordic Rheology Society. 21, 341-346 (2013).</li><li>Gilmore, B. F., Hamill, T. M., Jones, D. S., Gorman, S. 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The authors declare that they have no conflicts of interest.

The MBEC assay (biofilm microplate assay) was the first method to be recognized as a standard biofilm eradication test by the ASTM17. Our study and others have shown that there are two critical steps when using this assay: the sonication step (time and power) and the disinfectant treatment time18. Stewart and Parker also suggested other parameters that could influence the outcome of the assay, such as the microbial species, biofilm age, surface area/volume ratio, etc.<sup c...

The dairy industry is a major industrial sector worldwide, including in Canada, where there are more than 10,500 dairy farms producing nearly 90 million hL of milk each year1. Despite the strict hygiene requirements imposed in the dairy industry, including in processing plants, milk constitutes a great culture medium for microorganisms, and thus, dairy products are likely to contain microorganisms, including spoilage or pathogenic microorganisms. These pathogens can cause various diseases; for example, Salmonella sp. and Listeria monocytogenes can cause gastroenteritis and meningitis, respectively2. Spoilage microorganisms can affect the quality and organoleptic properties of dairy products by producing gases, extracellular enzymes, or acids3. The appearance and color of the milk may also be altered, for example by Pseudomonas spp.4.
Some of these microorganisms can form biofilms on different surfaces, including stainless steel. Such biofilms enable the persistence and multiplication of microorganisms on the surface of the equipment and, thus, the contamination of the dairy products5. Biofilms are also problematic because of their ability to impede heat transfer and accelerate the corrosion of the equipment, leading to premature replacement of the equipment and, thus, to economic losses6.
Clean-in-place (CIP) procedures allow the food industry to control the growth of microorganisms. These procedures involve the sequential use of sodium hydroxide, nitric acid, and, sometimes, sanitizers containing hypochlorous acid and peracetic acid7,8. Although hypochlorous acid is highly effective against microorganisms, it also reacts with natural organic matter, causing the formation of toxic by-products9. Peracetic acid does not generate harmful by-products10; however, its effectiveness against biofilms in the food industry is highly variable10,11. Recently, other peroxyacids, including perpropionic and perlactic acids, have been studied for their antimicrobial activity, and they appear to be a good alternative for the control of microbial growth in biofilms12,13.
Therefore, this study aimed to evaluate the efficacy of organic peroxyacids (peracetic, perpropionic, and perlactic acids and a peracetic acid-based disinfectant) for eradicating dairy biofilms using an approach combining the minimum biofilm eradication concentration (MBEC) assay, a static high-throughput screening method, and the Center for Disease Control (CDC) biofilm reactor, a dynamic method that mimics in situ conditions. The MBEC assay is hereafter referred to as "biofilm microtiter plates" in the protocol. The protocol presented here and the representative results demonstrate the efficacy of organic peroxyacids and their potential application for controlling microbial biofilms in the dairy industry.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >0.2 &#181;m filters&#160;</td>
			<td >Corning</td>
			<td >09-754-28</td>
			<td >diameter: 50 mm, PTFE- Membrane</td>
		</tr>
		<tr >
			<td >316 stainless-steel disc coupon</td>
			<td >Biosurface Technologies Corporation</td>
			<td >RD128-316</td>
			<td></td>
		</tr>
		<tr >
			<td >316 stainless-steel slide coupon</td>
			<td >Biosurface Technologies Corporation</td>
			<td >CBR 2128-316</td>
			<td></td>
		</tr>
		<tr >
			<td >96-microtiter plate</td>
			<td >Corning</td>
			<td >07-200-89</td>
			<td>cell Culture-Treated, flat-Bottom Microplate&#160;</td>
		</tr>
		<tr >
			<td >Acetic acid</td>
			<td >Sigma Aldrich</td>
			<td >27225</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Aluminium stubs</td>
			<td >Electron Microscopy Science</td>
			<td >75830-10</td>
			<td>32x5mm</td>
		</tr>
		<tr >
			<td >Aqueous glutaraldehyde EM Grade 25%</td>
			<td >Electron Microscopy Sciences</td>
			<td >16220</td>
			<td>store at -20 &#176;C</td>
		</tr>
		<tr >
			<td >AB204-S/FACT Analytical balance</td>
			<td >Mettler Toledo</td>
			<td >AB204-S</td>
			<td></td>
		</tr>
		<tr >
			<td >Bacterial Vent Filter (0.45 &#181;m)</td>
			<td >Biosurface Technologies Corporation</td>
			<td >BST 02915</td>
			<td></td>
		</tr>
		<tr >
			<td >BioDestroy</td>
			<td >Groupe Sani Marc</td>
			<td >09-10215</td>
			<td>commercial peracetic acid-based disinfectant, store at RT</td>
		</tr>
		<tr >
			<td >Carboy LDPE 20 L</td>
			<td >Cole Parmer</td>
			<td >06031-52</td>
			<td></td>
		</tr>
		<tr >
			<td >CDC biofilm reactor</td>
			<td >Biosurface Technologies Corporation</td>
			<td >CRB 90</td>
			<td>bioreactor</td>
		</tr>
		<tr >
			<td >Cerium (IV) sulphate</td>
			<td >Thermo Scientific</td>
			<td >35650-K2</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Confocal laser scanning microscope&#160; LSM 700</td>
			<td >Zeiss</td>
			<td >LSM 700</td>
			<td></td>
		</tr>
		<tr >
			<td >Dey-Engley neutralizing broth</td>
			<td >Millipore</td>
			<td >D3435-500G</td>
			<td>store at 4 &#176;C</td>
		</tr>
		<tr >
			<td >EMS950x + 350s gold sputter&#160;</td>
			<td >Electron Microscopy Sciences</td>
			<td ></td>
			<td></td>
		</tr>
		<tr >
			<td >Epoxy resin</td>
			<td >Electron Microscopy Sciences</td>
			<td >14121</td>
			<td>with BDMA</td>
		</tr>
		<tr >
			<td >Ethyl alcohol 95%, USP</td>
			<td >Greenfield global</td>
			<td >P016EA95</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Ferroin indicator solution</td>
			<td >Sigma Aldrich</td>
			<td >318922-100ML</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Filling/venting cap</td>
			<td >Cole Parmer</td>
			<td >RK-06258-00</td>
			<td></td>
		</tr>
		<tr >
			<td >FilmTracer LIVE/DEAD Biofilm Viability Kit</td>
			<td >Invitrogen</td>
			<td >L10316</td>
			<td >fluorescent cell viability kit (SYTO 9: green fluorescent stain, Propidium iodide: red fluorescent stain), store at - 20 &#176;C</td>
		</tr>
		<tr >
			<td >Glass flow break</td>
			<td >Biosurface Technologies Corporation</td>
			<td >FB 50</td>
			<td></td>
		</tr>
		<tr >
			<td >Gold with silver paint&#160;</td>
			<td >Electron Microscopy Sciences</td>
			<td >12684-15</td>
			<td></td>
		</tr>
		<tr >
			<td >Heating plate set</td>
			<td >Biosurface Technologies Corporation</td>
			<td >110V Stir Plate</td>
			<td></td>
		</tr>
		<tr >
			<td >Hex screwdriver</td>
			<td >Biosurface Technologies Corporation</td>
			<td >CBR 5497</td>
			<td></td>
		</tr>
		<tr >
			<td >Hydrogen peroxide</td>
			<td >Sigma</td>
			<td >216763</td>
			<td>store at 4 &#176;C</td>
		</tr>
		<tr >
			<td >Inoculating loops</td>
			<td >VWR</td>
			<td >12000-812</td>
			<td>sterile, 10 &#181;l</td>
		</tr>
		<tr >
			<td >Lactic acid</td>
			<td >Laboratoire MAT</td>
			<td >LU-0200</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >MASTERFLEX L/S 7557-04 W/ 7557-02 with EASY-LOAD II peristaltic pump and 77200-50 Head</td>
			<td >Cole Parmer</td>
			<td >77200-60</td>
			<td></td>
		</tr>
		<tr >
			<td >MBEC (Minimum Biofilm Eradication Concentration) assay biofilm inoculator with a 96-well base</td>
			<td >Innovotech</td>
			<td >19111</td>
			<td>Biofilm microtiter plate</td>
		</tr>
		<tr >
			<td >Oxford agar base</td>
			<td >Thermo Scientific</td>
			<td >OXCM0856B</td>
			<td>store at 4 &#176;C</td>
		</tr>
		<tr >
			<td >Plastic coupon holder</td>
			<td >Biosurface Technologies Corporation</td>
			<td >CBR 2203</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic slide holder rod</td>
			<td >Biosurface Technologies Corporation</td>
			<td >CBR 2203-GL</td>
			<td></td>
		</tr>
		<tr >
			<td >Potassium iodide</td>
			<td >Fisher Chemical</td>
			<td >P410-500</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Precision slotted screwdriver (1.5 mm x 40 mm)</td>
			<td >Wiha</td>
			<td >26015</td>
			<td></td>
		</tr>
		<tr >
			<td >Propionic acid</td>
			<td >Laboratoire MAT</td>
			<td >PF-0221</td>
			<td>store at RT</td>
		</tr>
		<tr >
			<td >Sartorius BCE822-1S Entris&#174; II Basic Essential Toploading Balance</td>
			<td >Cole Parmer</td>
			<td>&#160;UZ-11976-3</td>
			<td></td>
		</tr>
		<tr >
			<td >Scanning electron microscope JSM-6360LV model</td>
			<td >JEOL</td>
			<td >JSM-6360LV</td>
			<td>SEM and user control interface</td>
		</tr>
		<tr >
			<td >Screw cap tube, 15 mL</td>
			<td >Sarstedt</td>
			<td >62.554.205</td>
			<td>(Lx&#216;): 120 x 17 mm, material: PP, conical base, transparent, HD-PE</td>
		</tr>
		<tr >
			<td >Screw cap tube, 50 mL</td>
			<td >Sarstedt</td>
			<td >62.547.205</td>
			<td>(Lx&#216;): 114 x 28 mm, material: PP, conical base, transparent, HD-PE</td>
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			<td >Sodium Cacodylate Trihydrate</td>
			<td >Electron Microscopy Sciences</td>
			<td>&#160;12300</td>
			<td>store at -20 &#176;C</td>
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			<td >Sodium thiosulfate</td>
			<td >Thermo Scientific</td>
			<td >AC124270010</td>
			<td>store at RT</td>
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			<td >Sonication bath</td>
			<td >Fisher</td>
			<td >15-336-122</td>
			<td>5,7 L</td>
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			<td >Starch solution</td>
			<td >Anachemia</td>
			<td >AC8615</td>
			<td>store at RT</td>
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			<td >Sulfuric acid</td>
			<td >Sigma Aldrich</td>
			<td >258105-500ML</td>
			<td>store at RT</td>
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			<td >Tryptic soy agar</td>
			<td >BD Bacto</td>
			<td >DF0369-17-6</td>
			<td>store at RT</td>
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			<td >Tryptic soy broth</td>
			<td >BD Bacto</td>
			<td >DF0370-17-3</td>
			<td>store at RT</td>
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			<td >Tubing Masterflex L/S 16 25&#39;</td>
			<td >Cole Parmer</td>
			<td >MFX0642416</td>
			<td></td>
		</tr>
		<tr >
			<td >Tubing Masterflex L/S 18 25&#39;</td>
			<td >Cole Parmer</td>
			<td >MFX0642418</td>
			<td></td>
		</tr>
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			<td >Tygon SPT-3350 silicon tubing&#160;</td>
			<td >Saint-Gobain</td>
			<td >ABW18NSF</td>
			<td>IDx OD: 1/4 in.x 7/16 in.</td>
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			<td >Vortex</td>
			<td >Cole Palmer</td>
			<td >UZ-04724-00</td>
			<td></td>
		</tr>
		<tr >
			<td >Water bath&#160;</td>
			<td >VWR</td>
			<td >89202-970</td>
			<td></td>
		</tr>
		<tr >
			<td >Zen software</td>
			<td >Zeiss</td>
			<td ></td>
			<td></td>
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evaluation of the efficacy of organic peroxyacids for eradicating dairy biofilms using an approach combining static and dynamic methods

The presence of biofilms in the dairy industry is of major concern, as they may lead to the production of unsafe and altered dairy products due to their high resistance to most clean-in-place (CIP) procedures frequently used in processing plants. Therefore, it is imperative to develop new biofilm control strategies for the dairy industry. This protocol is aimed at evaluating the efficacy of organic peroxyacids (peracetic, perpropionic, and perlactic acids and a commercial peracetic acid-based disinfectant) for eradicating dairy biofilms using a combination of static and dynamic methods. All the disinfectants were tested on the strongest biofilm-producing bacteria in either a single or a mixed biofilm using the minimum biofilm eradication concentration (MBEC) assay, a static high-throughput screening method. A contact time of 5 min with the disinfectants at the recommended concentrations successfully eradicated both the single and mixed biofilms. Studies are currently ongoing to confirm these observations using the Center for Disease Control (CDC) biofilm reactor, a dynamic method to mimic in situ conditions. This type of bioreactor enables the use of a stainless-steel surface, which constitutes most industrial equipment and surfaces. The preliminary results from the reactor appear to confirm the efficacy of organic peroxyacids against biofilms. The combined approach described in this study may be used to develop and test new biological or chemical formulations for controlling biofilms and eradicating microorganisms.

The SEM analysis shows the presence of biofilms produced by P. azotoformans PFl1A on the biofilm microplate pegs (Figure 2A). A three-dimensional biofilm structure can be observed. The P. azotoformans PFl1A was previously identified as a strong biofilm producer (A570 &#62; 1.5) using 96-well microtiter plates12.
In addition, the P. azotoformans PFl1A biofilm that formed on a stainless-steel slide using ...

Watch this Scientific Journal Video about Evaluation of the Efficacy of Organic Peroxyacids for Eradicating Dairy Biofilms Using an Approach Combining Static and Dynamic Methods at JoVE.com

Evaluation of the Efficacy of Organic Peroxyacids for Eradicating Dairy Biofilms Using an Approach Combining Static and Dynamic Methods

This protocol describes an approach combining static and dynamic methods to evaluate the efficacy of organic peroxyacids for eradicating biofilms in the dairy industry. This approach may also be used to test the effectiveness of new biological or chemical formulations for controlling biofilms.

The presence of biofilms in the dairy industry is of major concern, as they may lead to the production of unsafe and altered dairy products due to their ...

Biofilm forming microorganism are a major issue in the food industry, including the dairy industry. Because of their negative impact on the quality of the products, then it is important to develop biofilm control strategies. This approach combines a static high-throughput screening method and a dynamic method that mimics in situ conditions.These two methods are complementary for studying the efficacy of disinfectants against biofilms. This approach can be used to test new biological or chemical formulations to control biofilms in the food, medical, or environmental sectors. Begin by vortexing the Pseudomonas azotoformans bacterial culture tubes.Aseptically transfer 100 microliters of the bacterial culture into 10 milliliters of sterile tryptic soy broth or TSB medium to achieve the final concentration of approximately two times 10 to the seventh CFU per milliliter. Vortex the culture tube. Then using a multichannel pipette, transfer 150 microliters of the diluted bacterial culture in the biofilm microtiter plate wells in triplicate.Load 150 microliters of TSB medium into three new wells as control. Next, incubate the biofilm microtiter plate at 30 degrees Celsius for 24 hours without agitation. Clean and air dry the parts of the bioreactor before placing the flat blade inside the one liter glass beaker attached to the holder by a magnetic bar.Maintain the setup upright using the plastic bar attached to the inner side of the bioreactor lid. Use the screwdriver to place the stainless steel coupons or slides on their polypropylene rods. Insert coupons or slides into the holes in the lid without placing their alignment pins in the notches allowing steam to escape during sterilization.Cover all the bioreactor vents with aluminum foil and wrap the rest of the equipment, namely the size 18 tubing and the size 16 tubing, the glass flow brake, the container caps, the screwdrivers, the forceps, and 0.2 micrometer filters with aluminum foil. Autoclave the bioreactor set up in a dry cycle at 121 degrees Celsius for 20 minutes. To perform the first step of the biofilm formation in the bioreactor in batch mode, inside a biological safety cabinet, connect one end of the size 18 tubing to the outlet spout of the bioreactor and keep the other end wrapped in aluminum foil.Remove one coupon or slide holder from the bioreactor lid and place it in a sterile 50 milliliter tube. Then using a 50 milliliter serological pipette, fill the bioreactor beaker with 340 milliliters of 300 milligrams per milliliter TSB medium through the hole occupied by the rod. To inoculate the culture medium in the bioreactor, add one milliliter of 10 to the eighth CFU per milliliter Pseudomonas azotoformans bacterial solution through the orifice using a five milliliter pipette and place the rod back into its original position.Position the rods already placed in the lid holes for the pins to fit into the respective notches. Then place a 0.2 micrometer bacterial air purge filter at the end of the smallest diameter tube located on the lid of the bioreactor. The other tube of the same diameter remains permanently plugged with a metal screw cap or a silicone plug that closes tightly.Place the bioreactor for 24 hours over the heating plate set at 30 degrees Celsius and stir at 130 RPM. After 24 hours, perform the second step of the biofilm formation in the bioreactor in continuous flow mode. Place a carboy containing 18 liters of sterile distilled water in the biosafety cabinet.Then add two liters of 1000 milligrams per liter TSB culture medium to obtain a final concentration of 100 milligrams per liter. Cover the container with its sterile cap to which two tubes are connected. The first one is a silicone tube fixed on the cap's interface to pump the medium.The second one the size 16 tubing is connected to the external port allowing the liquid to flow toward the bioreactor. After connecting the size 16 tubing to the extremity of the glass flow brake, insert the latter into the largest tube on the lid of the bioreactor by its other end and then install the size 16 tubing in the peristaltic pump. Use another 20 liter carboy to collect the effluent from the bioreactor.Attach the end of the tube connected to the bioreactor outlet spout to the cap of the waste container. Insert a 0.2 micrometer filter into the tube present on the lid of this container. Once done, start the peristaltic pump at a flow rate of 11.3 milliliters per minute and leave the system running for 24 hours.After 24 hours, turn off the peristaltic pump and stop stirring and heating the bioreactor. To recover the bacterial biofilm, rinse the coupons or slides in 40 milliliters of PBS to eliminate planktonic bacteria. Then release them into a sterile 50 milliliter conical tube containing 40 milliliters of PBS.After 30 seconds of vortexing, sonicate the tubes at 40 kilohertz for 30 seconds. Repeat this three times. Once done, collect the 40 milliliters of biofilm suspension in a sterile 50 milliliter conical tube and rinse the coupons or slides with two of sterile PBS solution.Recover this rinsing liquid and add it to the already collected biofilm suspension. Take out the microtiter plate from 30 degrees Celsius. Add 200 microliters of PBS into three wells of a 96-well microplate.To wash the biofilms and eliminate planktonic bacteria, transfer the lid of the biofilm microplate with biofilms formed on the pegs to the 96-well microplate containing the PBS for 10 seconds. Prepare the disinfectants at the required concentrations and add 200 microliters of each disinfectant concentration into the wells of a new 96-well microtiter plate in triplicate. Transfer the lid of the biofilm microtiter plate onto the 96 well-microtiter plate containing the disinfectants and incubate the plate at room temperature for the desired exposure time.Next, add 200 microliters of Dey-Engley neutralizing broth to the wells of a new 96-well microtiter plate. Transfer the lid of the biofilm microtiter plate to the 96-well microtiter plate containing the neutralizing broth. Seal the microtiter plate with parafilm and place it in the bath sonicator at 40 kilohertz for 30 minutes.After 30 minutes, from the first column of the sonicated plate, transfer 100 microliters of detached biofilms to the first row of a new 96-well microtiter plate. Then add 180 microliters of sterile PBS to a 96-well plate except for the first row. Next, transfer 20 microliters of the biofilm solution from the first row to the wells in the second row containing 180 microliters of PBS to achieve the dilution 10 to the minus one.Then transfer 20 microliters from the second row to the wells in the next row to achieve the dilution of 10 to the minus two. Repeat this to obtain dilution between 10 to the minus five and 10 to the minus seven. Inoculate 100 microliters of the desired dilution on TSA and incubate the plates as per the growth parameters of the bacterium.Form the Pseudomonas azotoformans PFLA 1 biofilms on the coupons in the bioreactor, remove the rod holding the coupons and rinse the rod inside a conical tube containing 30 milliliters of PBS to remove planktonic cells. Drop each coupon into a sterile 50 milliliter conical tube using a screwdriver. Then add four milliliters of the appropriate organic peroxyacid solution or PBS for the control.After five minutes of incubation, add 36 milliliters of Dey-Engley neutralizing broth. After vortexing the conical tube for 30 seconds, sonicate them at 40 kilohertz for 30 seconds. Repeat the process three times to obtain the biofilm suspension.Repeat the same procedure with the other rods, prepare serial delusions of the biofilm suspension, and plate the suspension on TSA medium as described earlier. The SCM analysis showed the presence of the biofilm by Pseudomonas azotoformans PFL1A on the biofilm microplate pegs. The Pseudomonas azotoformans PFL1A biofilm formed on a stainless steel slide using a bioreactor appeared very dense and displayed the morphological characteristics of a mature three-dimensional biofilm.The results of the bacterial counts of the biofilms developed by this isolate in the dynamic system showed significant cell densities corresponding to 8.74 log CFU per centimeter square in TSB culture medium and 7.86 log CFU centimeter square in sterile skim milk. The results obtained with the B.vesicularis isolate showed that the increase in the nutrient concentration from 100 to 900 milligrams per liter resulted in an increase in the bacterial count of the biofilms from 6.11 to 8.71 log CFU centimeter square. Also, significant biofilm growth was observed when the flow rate was reduced to 6.0 milliliter per minute, indicating that certain factors could influence biofilm formation in the bioreactor.None of the biofilms contained detectable viable cells at five minutes contact time in 500 parts per million with organic peroxyacids and 100, 000 parts per million with hydrogen peroxide concentrations of disinfectants usually applied in dairy plants. The SCM showed the three-dimensional structure of untreated minimum biofilm eradication concentration or MBEC biofilms, while the treated MBEC biofilms lost their three-dimensional conformation. It is essential to remain under the sterile condition while performing this protocol.Also, user must remember that generated result are associated with a unique isolate and disinfectant. Combining disinfectant with mechanical vibration, ultrasound, or enzymatic treatments could be evaluated to improve the efficacy of biofilm eradication. This approach using static and dynamic methods to form biofilms paved the way for researchers to screen and study new anti-biofilm formulation to better control biofilms in various sectors.

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Biology

1.4K vistas.  Université Laval. Los microorganismos formadores de biopelículas son un problema importante en la industria alimentaria, incluida la industria láctea. Debido a su impacto negativo en la calidad de los productos, entonces es importante desarrollar estrategias de control de biopelículas. Este enfoque combina un método de cribado estático de alto rendimiento y un método dinámico que imita las condiciones in situ.Estos dos métodos son complementarios para estudiar la eficacia de los desinfectantes c...