Abstract
Bacterial spoilage of food products is regulated by density dependent communication system called quorum sensing (QS). QS control biofilm formation in numerous food pathogens and Biofilms formed on food surfaces act as carriers of bacterial contamination leading to spoilage of food and health hazards. Agents inhibiting or interfering with bacterial QS and biofilm are gaining importance as a novel class of next-generation food preservatives/packaging material. In the present study, Zinc nanostructures were synthesised using Nigella sativa seed extract (NS-ZnNPs). Synthesized nanostructures were characterized hexagonal wurtzite structure of size ~24 nm by UV-visible, XRD, FTIR and TEM. NS-ZnNPs demonstrated broad-spectrum QS inhibition in C. violaceum and P. aeruginosa biosensor strains. Synthesized nanostructures inhibited QS regulated functions of C. violaceum CVO26 (violacein) and elastase, protease, pyocyanin and alginate production in PAO1 significantly. NS-ZnNPs at sub-inhibitory concentrations inhibited the biofilm formation of four-food pathogens viz. C. violaceum 12472, PAO1, L. monocytogenes, E. coli. Moreover, NS-ZnNPs was found effective in inhibiting pre-formed mature biofilms of the four pathogens. Therefore, the broad-spectrum inhibition of QS and biofilm by biogenic Zinc oxide nanoparticles and it is envisaged that these nontoxic bioactive nanostructures can be used as food packaging material and/or as food preservative.
Highlights
Major problem concerning the food industry is microbial spoilage of food and severe economic losses are incurred as result of microbial spoilage and/or contamination of food items with pathogens[1]
acyl-homoserine lactones (AHLs) based Quorum sensing (QS) regulates the production of violacein pigment in Chromobacterium violaceum, virulence in Pseudomonas aeruginosa, flagellar motility in Listeria monocytogenes, bioluminescence in Vibrio harveyi and V. fischeri, sporulation, cell differentiation and community organization which lead to the development of the mature biofilms[6,7]
C. violaceum 12472, C. violaceum CVO26 and P. aeruginosa PAO1 strains were cultivated at 28 °C and 37 °C respectively
Summary
Major problem concerning the food industry is microbial spoilage of food and severe economic losses are incurred as result of microbial spoilage and/or contamination of food items with pathogens[1]. Quorum sensing or cell-to-cell communication between bacteria commonly associated with contamination of food takes place by the production of signaling molecules called autoinducers and this bacterial cross talk can be intra as well inter species specific[4]. There is an urgent need to understand the role of quorum-sensing signaling molecules involved in food spoilage and develop novel, safe QS inhibitors that can interfere with bacterial signaling system and prevent food spoilage and biofilm formation by food-related bacteria. Three major types of autoinducers have been recognized: acyl-homoserine lactones (AHLs), autoinducing peptides (AIPs) and autoinducer-2 (AI-2s) molecules[5] These signal molecules regulate the production of various functions like pectinase, protease, siderophore-mediated iron chelation, characteristics associated with food spoilage[2]. This biogenic green synthesis approach involves the biomolecules such as proteins, amino acids, enzymes, vitamins, alkaloids, phenolics, saponins, tannins, and terpinoids, present in plant extracts, for reduction and stabilization of metal ions[17]
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