Antimicrobial activity of glycolic acid and glyoxal against Bacillus cereus and Pseudomonas fluorescens.

The development of effective disinfection strategies, including the search for new active biocides, is a priority research for the food industry. Glycolic acid (GA) and glyoxal (GO) are two glycolysis by-products approved as biocides for surface disinfection, whose antimicrobial action remains to be understood. This study focused on the understanding of the antimicrobial activity of GA and GO against two foodborne pathogens, Bacillus cereus and Pseudomonas fluorescens. Benzalkonium chloride (BAC) and peracetic acid (PAA) were used as reference biocides for comparison. The influence of biocide concentration and exposure time on the antimicrobial activity of the selected biocides was evaluated based on the European Standard EN 1276. The mode of action of each biocide was characterized based on their effects on the cell envelope and cell replication. According to the Chick-Watson model, all biocides interacted chemically with cell targets of both bacteria, except GO that only stablished physicochemical interactions with P. fluorescens. The survival curves revealed that high concentrations of biocide induced readily effects on cell culturability. The susceptibility profile of P. fluorescens was constant over time. In general, B. cereus increased tolerance to BAC and became more susceptible to cumulative damages of GA. Overall, this study demonstrates that the biocidal activity was species-, dose- and time-dependent. GA, similarly to BAC, was a membrane-active and oxidant agent. GO had no effect on the bacterial surface as well as PAA. GO was mainly categorized as a cell replication inhibitor. For the first time, the antimicrobial activity of GA and GO were characterized revealing their potential for rational combination with other biocides commonly used in the food industry.