## Materials and Methods
### Isolation of LAB and Bifidobacterium
The precipitate was stored at 4 \({}^{\circ}\)C for 18 h. Subsequently, the precipitate was collected after centrifugation at 10,000\(\times\)\(g\) for 30 min and dissolved in a minimum amount of deionized water. The agar diffusion bioassay was used to screen for bacteriocin-producing LAB or _Bifidobacterium_ strains among the 49 isolates from honeycomb filled with oregano honey, against selected (the most typical) bacterial pathogens and spoilage, isolated from fresh fruits and vegetables purchased in open markets and retail stores. These comprised: 3 _E. coli_ strains, 2 _Salmonella_ spp. strains, 2 _L. monocytogenes_ strains, 2 _B. cereus_ strains, 2 _Erwinia_ spp. strains and 1 _Xanthomonas_ spp. strain. Targeted indicator organisms were used as reference: _L. innocua_ (ATCC 33090 TM), _E. coli_ 0157:H7 (ATCC 69373) [17; 46]. One milliliter of each pathogen or spoilage fruits or vegetables organism (approximately 7 \(\times\) 10\({}^{5}\) cfu/L) was inoculated into 15 mL of semisolid BHI agar (BHI broth powder), supplemented with 0.7% agar (Merck) maintained at 50 \({}^{\circ}\)C and then poured into a Petri dish. After solidification, three wells of 5 mm diameter and 2 mm depth were made in the agar. (a) In the first well, 50 \(\upmu\)L of the untreated CFS aliquot from each LAB or _Bifidobacterium_ isolate were added. (b) The CFS was treated further and was adjusted to pH 6.0 with 1 mol/L NaOH in order to rule out possible observed antibacterial activity caused by acid formation. Then, 50 \(\upmu\)L of the pH-adjusted CFS were filtered and added to the second well. (c) The neutralized CFS described above was then treated with a final concentration of 1 mg mL\({}^{-1}\) of catalase (Merck) at 20-25 \({}^{\circ}\)C for 30 min to eliminate the possible inhibitory action of H\({}_{2}\)O\({}_{2}\). It was filtered and immediately was placed in the third well. In summary, if inhibition zones were present in the third well, the LAB or _Bifidobacterium_ isolates were considered to be able to produce bacteriocin-like inhibitory substances (BLIS). The BHI plates were incubated aerobically at 37 \({}^{\circ}\)C for 24 h or anaerobically at 37 \({}^{\circ}\)C for 24 h (in order to obtain the ideal growth requirements for each strain). The inhibition zone was measured using an electronic caliper with a digital display [15; 41]. Each screening test for the bacteriocin was performed in triplicate and the results are reported as mean values. The isolated crude CFS was evaluated to discover whether inhibition was due to BLIS. For that purpose, the selected enzymes were tested on the cell-free supernatant. The CFS displaying antimicrobial potential after acid neutralization and H\({}_{2}\)O\({}_{2}\) elimination was treated with proteolytic enzymes, among others, including trypsin, pepsin, lipase and \(\alpha\)-amylase. The proteolytic enzymes were dissolved in 40 mM Tris-HCl (pH, 8.2), 0.002 M HCl (pH, 7) and 0.05 M sodium phosphate (pH, 7.0), respectively, to a concentration of 0.1 mg mL\({}^{-1}\), while lipase and \(\alpha\)-amylase were dissolved in 0.1 M potassium phosphate (pH, 6.0) and 0.1 M potassium phosphate (pH, 7.0), respectively, to a final concentration of 0.1 mg/mL. Equal aliquots of both filter-sterilized CFS of each test strain and enzyme solution were mixed. Each enzyme was incubated at 37 \({}^{\circ}\)C for 2 h and heated to 100 \({}^{\circ}\)C for 5 min to inactivate the enzymes. These sample mixtures and controls (without enzyme treatment) were inoculated with the indicator strains _L. innocua_ (ATCC 33090 TM), _E. coli_ 0157:H7 (ATCC 69373). The treated inoculated CFS aliquots were then incubated in a solution at 37 \({}^{\circ}\)C for 2 h, after which the retention of bacteriocin-like substances (BLS) in the treated samples was determined by the agar diffusion method as described above. If the antibacterial activity was negative after the enzymatic treatment, the isolate was regarded as positive for producing a bacteriocin [47; 48].