Abstract
Currently, the health benefits of probiotic bacteria are well known, and this has taken up a great deal of space in food science and health, both research and operational. On the other hand, anti-biofilm properties on food pathogens in the food and pharmaceutical industries have created an attractive challenge. This study aimed to describe the inhibitory activity of cell-free supernatants (CFS), planktonic cells, and biofilm form of lactobacilus strains (L. rhamnosus and L. plantarum) against food pathogens such as Pseudomonas aeruginosa and Listeria monocytogenes. Anti-bacterial activities of the CFS of lactobacillus strains were assessed by the microplate method and via violet staining. Evaluation of the antagonistic activity of planktonic cells and biofilm of LAB were performed by the spread plate method. The results showed the incubation time of 48 h was the best time to produce biofilm. Although the planktonic states reduce the pathogens bacterial about 1 –1.5 log, but in biofilm forms, decreased L. monocytogenes about 4.5 log compared to the control, and in the case of P. aeruginosa, a growth reduction of about 2.13 log was observed. Furthermore, biofilm formation of L. monocytogenes in the presence of L. rhamnosus cell-free supernatant was more weakly than L. plantarum CFS, but their CFS effect on reducing the bacterial population of P. aeruginosa was the same. According to the study, biofilm produced by probiotic strains can be considered a new approach for biological control. Also, cell-free supernatant can be used as postbiotic in the food and pharmaceutical industries.
Highlights
Food safety is one of the most important issues for food producers and consumers
Biofilm The results demonstrated that the presence of L. rhamnosus, and L. plantarum biofilm, decreased L. monocytogenes by about 4.5 log compared to the control
In this study, two strains of lactic acid bacteria were examined, and their potential for biofilm production was measured. Both strains were able to grow in the microplate and mature biofilm formation, and there was a slight difference in the biofilm density of the strains (Figs. 2, 3)
Summary
Food safety is one of the most important issues for food producers and consumers. As food supply has become increasingly global, food safety issues need more attention (Moradi et al 2020). For this purpose, a new approach of researchers and industries in recent years has been using biological policies in the face of the challenge of foodborne pathogens. Speranza et al 2020) Since this phenomenon is straightforward and inherent in bacteria itself, it can be used as an intelligent technique to control food pathogens (Balaure and Grumezescu 2020). L. rhamnosus and L. plantarum are probiotic strains that have biofilm formation capacity and produced more robust biofilms than other species (Lebeer et al 2007a, b; Simoes et al 2009; Bujňáková and Kmeť 2012; Léonard et al 2014)
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