The glycolysis by-products glycolic acid and glyoxal cause antimicrobial and antibiofilm effects
Authors: Fernandes Susana , Simões Manuel 
Published: July 2020

&lt;p&gt;The development of new biocidal formulations targeting cells in biofilms is still a scientific challenge &lt;sup&gt;1,2&lt;/sup&gt;. The current arsenal of biocides is clearly limited in controlling biofilms &lt;sup&gt;3&lt;/sup&gt;. Therefore, novel molecules to control biofilms are needed. This study assessed the antimicrobial activity of glycolic acid (GA) and glyoxal (GO) against &lt;em&gt;Bacillus cereus&lt;/em&gt; and &lt;em&gt;Pseudomonas&amp;#160;fluorescens&lt;/em&gt;, two species commonly found in industrial biofilms. GA and GO are two glycolysis by-products approved as biocides for surface disinfection, whose antimicrobial action remains to be understood. Their antimicrobial activity was determined according to the European Standard EN&amp;#160;1276 &lt;sup&gt;4&lt;/sup&gt;. The mode of action was assessed according to the effects on the cell envelope (surface hydrophobicity and cell membrane damages) and cell replication. &lt;em&gt;P.&amp;#160;fluorescens&lt;/em&gt; was eradicated by both selected compounds, while &lt;em&gt;B.&amp;#160;cereus&lt;/em&gt; was only partially reduced even under high concentrations. According to the survival curves, &lt;em&gt;P.&amp;#160;fluorescens&lt;/em&gt; cells had the same susceptibility to both compounds.&lt;em&gt; B.&amp;#160;cereus&lt;/em&gt; cells were more susceptible due to cumulative damages. The dose-activity curves proposed that the selected compounds interacted chemically with cell targets - GA and GO were able to disturb cell integrity, causing changes in cell hydrophobicity and further membrane damages. In terms of cell replication, GA caused negligible changes in lag time length and in the maximum cell growth, while GO was found to act as a bacteriostatic. Thus, GA was found to be an oxidant (acid group) and membrane-active compound (alcohol group). On the other hand, GO had cell growth inhibitory (nucleophilic group) effects. These compounds were further applied against&lt;em&gt; B. cereus&lt;/em&gt; and &lt;em&gt;P. fluorescens&lt;/em&gt; biofilms, promoting strong inactivation and removal effects. The combination of GA and GO with traditional biocides is likely to represent a new, and much needed, generation of disinfectant formulations for industrial biofilm control.&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;1 Yuksel, F. N., Buzrul, S., Akcelik, M. &amp; Akcelik, N. Inhibition and eradication of &lt;em&gt;Salmonella&lt;/em&gt; Typhimurium biofilm using P22 bacteriophage, EDTA and nisin. Biofouling &lt;strong&gt;34&lt;/strong&gt;, 1046-1054, doi:10.1080/08927014.2018.1538412 (2019).&lt;/p&gt;
&lt;p&gt;2 Ara&amp;#250;jo, P. A. et al. Combination of selected enzymes with cetyltrimethylammonium bromide in biofilm inactivation, removal and regrowth. Food Res Int &lt;strong&gt;95&lt;/strong&gt;, 101-107, doi:10.1016/j.foodres.2017.02.016 (2017).&lt;/p&gt;
&lt;p&gt;3 Capita, R. et al. Effect of low doses of biocides on the antimicrobial resistance and the biofilms of &lt;em&gt;Cronobacter sakazakii&lt;/em&gt; and &lt;em&gt;Yersinia enterocolitica&lt;/em&gt;. Sci Rep &lt;strong&gt;9&lt;/strong&gt;, 15905, doi:10.1038/s41598-019-51907-1 (2019).&lt;/p&gt;
&lt;p&gt;4 European Standard EN-1276 Chemical disinfectants and antiseptics in: Quantitative suspension test for the evaluation of bactericidal activity of chemical disinfectants and antiseptics used in food, industrial, domestic, and institutional areas - Test method and requirements (phase 2, step 1) (2009).&lt;/p&gt;