Identification and characterization of two bacteriocin-producing bacteria isolated from garlic and ginger root

Two bacteriocin-producing bacterial strains were isolated from garlic and g inger root by the agar overlay method. The bacteria were identified by 16S rRNA sequence analyses and fermentation patterns as Leuconostoc mesenteroid es (garlic isolate) and Lactococcus lactis (ginger isolate). The bacterioci ns were assigned the names leucocin BC2 and lactocin GI3, respectively. Phy siochemical properties and antimicrobial spectra of the bacteriocins were d etermined by the spot-on-lawn method. Both bacteriocins were inhibited by p roteolytic enzymes. Leucocin BC2 exhibited a narrow antimicrobial spectrum, inhibiting only Bacillus, Enterococcus, and Listeria species. Lactocin GI3 had a broader spectrum, inhibiting Bacillus, Clostridium, Listeria, Entero coccus, Leuconostoc, Pediococcus, and Staphylococcus species. Both bacterio cins remained active when heated at 90 degrees C for 15 min or 120 degrees C for 20 min. Leucocin BC2 assayed at 37 degrees C showed an inhibitory act ivity of 1,600 AU/ml, whereas at 8 degrees C the activity was 12,800 AU/ml. Conversely, lactocin GI3 activity was the same at both assay temperatures. Both bacteriocins remained active over a pH range of 2.0 to 9.0 and in var ious organic solvents. The activity of leucocin BC2 was increased when trea ted with 0.5% acetic acid and 0.5% lactic acid, whereas lactocin GI3 activi ty was decreased with either acid. The molecular mass values were 3.7 kDa f or leucocin BC2 and 3.9 kDa for lactocin GI3. These results show that the i nhibitory substances produced by the bacteria isolated from garlic and ging er are bacteriocins that appear to be different in some characteristics fro m previously reported bacteriocins.