Abstract
A mixed culture (polymicrobial) biofilm provides a favorable environment for pathogens to persist in the food processing environment and to contaminate food products. Inactivation and eradication of such biofilms from food processing environments are achieved by using harsh disinfectants, but their toxicity and environmentally hostile characteristics are unsustainable. This study aims to use food-grade natural nanoparticulated antimicrobials to control mixed-culture biofilms. Chitosan, a natural broad-spectrum antimicrobial biopolymer (polysaccharide) from crustaceans, was derivatized to produce chitosan nanoparticles (ChNP) as a carrier for another broad-spectrum antimicrobial agent, ε-poly-L-lysine (PL), to synthesize ChNP-PL conjugate. The antimicrobial activity of ChNP and ChNP-PL was tested against mixed-culture biofilms. ChNP-PL (~100 nm) exhibited a synergistic antimicrobial and anti-biofilm effect against mono or mixed-culture biofilms of five foodborne pathogens, including Listeria monocytogenes, Staphylococcus aureus, Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Pseudomonas aeruginosa. ChNP-PL treatment prevented biofilm formation by mono or mixed cultures of L. monocytogenes, P. aeruginosa, and E. coli O157:H7, and bacterial counts were either below the detection limit or caused 3.5–5 log reduction. ChNP-PL also inactivated preformed biofilms. In monoculture biofilm, ChNP-PL treatment reduced L. monocytogenes counts by 4.5 logs, S. Enteritidis by 2 logs, E. coli by 2 logs, and S. aureus by 0.5 logs, while ChNP-PL had no inhibitory effect on P. aeruginosa. In vitro mammalian cell-based cytotoxicity analysis confirmed ChNP-PL to have no deleterious effect on intestinal HCT-8 cell line. In conclusion, our results show ChNP-PL has strong potential to prevent the formation or inactivation of preformed polymicrobial biofilms of foodborne pathogens.
Highlights
Licensee MDPI, Basel, Switzerland.A major public health concern for the food industry is foodborne illnesses, hospitalizations, loss of lives, and the associated recalls of food products leading to huge financial losses
We explored whether the antibiofilm activity of chitosan nanoparticles (ChNP) could be augmented with the addition of another broad-spectrum food-grade antimicrobial peptide, such as ε-poly-L-lysine [38]. ε-poly-L-lysine (PL) is a water-soluble, biodegradable, edible, and nontoxic homo-poly-amino acids (25–35 lysine residues, 2.85–3.98 kDa), linked by the peptide bond between the carboxyl and ε-amino groups of L-lysine [39]
Synthesis of Chitosan Nanoparticles Conjugated with ε-poly-L-lysine (ChNP-PL)
Summary
Licensee MDPI, Basel, Switzerland.A major public health concern for the food industry is foodborne illnesses, hospitalizations, loss of lives, and the associated recalls of food products leading to huge financial losses. Foodborne pathogens are responsible for two billion illnesses and over one million deaths annually [1], while in the US, about 48 million illnesses, 128,000 hospitalizations, and 3000 deaths happen annually with an estimated economic burden of about. The persistence of pathogens in food processing facilities has been considered the single most critical factor in product contamination [4]. Persistence is facilitated by biofilm formation by mono or mixed cultures [5,6,7]. From raw or undercooked food materials, pathogens find a harborage site or niche in food production facilities or product surfaces and form biofilms [9,12,13], which serve as a source for foodborne outbreaks, especially in cafeterias, hospitals, cruise ships, and commercial food processing facilities [14]
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