Studies on bacteriocinogenic Lactobacillus isolates from selected Nigerian fermented foods.

Ten bacteriocin-producing (bacteriocinogenic) Lactobacillus isolates obtained from three Nigerian fermented foods namely: kenkey, ogi and wara were tested against the following indicator organisms: Lactobacillus plantarum and food borne pathogens comprising enterotoxigenic Escherichia coli, enterohaemorrhagic Escherichia coli, Serratia, Pseudomonas, Vibrio cholerae, Aeromonas sobria, Aeromonas cavice, Salmonella typhimurium, Plesiomonas shigelloides and Staphylococcus aureus. All the bacteriocinogenic Lactobacillus were found to inhibit L. plantarum while some inhibited some of the food borne pathogens listed above. The antimicrobial activities of bacteriocins from L. plantarum KKY12 and L. casei OGM12 were caused by proteins detectable in the culture liquids. They are designated Plantacin N and Caseicin A and they have narrow antimicrobial spectra. Plantacin N from L. plantarum KKY12 was active against L. plantarum, Pseudomonas, Aeromonas sobria and Aeromonas cavice whereas Caseicin A from L. casei OGM12 inhibited L. plantarum, enterotoxigenic Escherichia coli and Vibrio cholerae. Caseicin A is stable at 121 degrees C/15 mins, and both are inactivated by proteolytic enzymes. The bacteriocinogenic properties of the local isolates of Lactobacillus can help to reduce hygienic risk and the spoilage of fermented foods.