Antibiofilm activity of glycolic acid and glyoxal and their diffusion-reaction interactions with biofilm components.

Biofilms on food-contact surfaces act as potential reservoirs of microbial pathogens and can cause operational problems. The search for effective biofilm control agents is a significant research need. In this study, glycolic acid (GA) and glyoxal (GO) were tested in the control of biofilms formed by Bacilluscereus and Pseudomonasfluorescens. Benzalkonium chloride (BAC) and peracetic acid (PAA) were used as reference biocides for industrial surface disinfection. The action of the selected biocides was assessed in bacterial motility, culturability, biofilm removal and inactivation, interference with biofilm components and limitation of biocide penetration through the biofilms (reaction-diffusion interactions). Bacterial motility was not affected by the exposure to sub-inhibitory biocide concentrations. In terms of antibiofilm activity, B.cereus biofilms were tolerant to the action of BAC, GA, and GO, with reductions of circa 2-log CFU/cm ² . Even 10000 µg/mL of PAA had modest effects against B. cereus biofilms (5-log CFU/cm ² ). On the other hand, P.fluorescens biofilms were more susceptible to the biocides, except BAC which was not effective. The minimum concentrations to cause 3-log CFU/cm ² reduction in P. fluorescens biofilms were 10000 µg/mL of PAA and GA, and 20000 µg/mL of GO. GO and BAC were the most actives for biofilm removal, while high biofilm inactivation was caused by GA and PAA. In general, biofilm components affected the antimicrobial activity of all the biocides. The activity of GA and GO was not notably diffusion-reaction limited in contrast to PAA. Overall, this study demonstrated that GA and GO had potential antibiofilm activity, being limited at a low level by physicochemical interactions with biofilm components.
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