Microencapsulation of reuterin to enhance long-term efficacy against food-borne pathogen Listeria monocytogenes

Abstract

The aim of this study was to microencapsulate the reuterin produced by Lactobacillus reuteri BPL-36 strain for its long-term efficacy against food-borne pathogen Listeria monocytogenes. Lactobacillus reuteri BPL-36 strain previously isolated from a human infant fecal sample in lab was selected for the present study based on its ability to produce reuterin. The organism displayed a broad-spectrum antimicrobial activity. Reuterin concentration of 89.63 mM was obtained in the MRS-glycerol medium after 16 h incubation at 37 °C. The reuterin concentration required to inhibit the growth of Pseudomonas aeruginosa, Escherichia coli O157: H7, Salmonella typhi, Staphylococcus aureus, and Listeria monocytogenes was found to be 1.0, 2.0, 2.0, 4.0, and 10.0 AU/mL, respectively. Microencapsulation of reuterin to enhance long-term efficacy against food-borne pathogens was done. Results in this study indicated that the release characteristics of reuterin from the encapsulated particles were pH dependent. The release characteristics were unaffected by the storage of encapsulated reuterin at 4 °C for 2 weeks. The anti-listerial efficacy of the encapsulated reuterin was tested against L. monocytogenes in the BHI medium adjusted to pH 5.0 with a reuterin content equivalent to 16 mM, similar to un-encapsulated (free) reuterin. Encapsulated reuterin demonstrated enhanced efficacy against L. monocytogenes for longer duration of time when compared with un-encapsulated (free) reuterin. The present work demonstrated a novel antimicrobial delivery system that ensured much better capability of inhibiting the growth of L. monocytogenes throughout 24 h incubation at 37 °C.

Keywords: Lactobacillus reuteri; Microencapsulation; Pathogens; Reuterin; Safety.

Fig. 1

Colorimetric quantification of reuterin produced by L. reuteri BPL-36 at different time intervals after incubation at 37 °C. Data points are means of triplicate readings with SEMs represented by vertical bars

Fig. 2

Morphology of microcapsules at 10× magnification

Fig. 3

pH-dependent release pattern of encapsulated reuterin during storage at 37 °C. Data points are means of triplicate OD₆₂₀ readings with SEMs represented by vertical bars

Fig. 4

pH-dependent release pattern of encapsulated reuterin during storage at 4 °C. Data points are means of triplicate OD620 readings with SEMs represented by vertical bars

Fig. 5

Log counts (CFU/mL, mean ± SD) of pathogens Listeria monocytogenes in BHI medium without or with free reuterin, encapsulated reuterin during incubation at 37 °C (reuterin 16 mM)