ABSTRACT

This study was carried out to extract and quantify the lactic acid bacteriocins from 'Ogiri' a locally fermented food. A total of nine (10) samples of Ogiri were purchased from local vendors who hawk the product around the Umuahia market. The serial dilution technique was employed in the inoculation of the Ogiri samples of which each of the samples was diluted in the 10-fold serial dilution technique. 0.1ml of the respective dilution (10^-7 and 10^-7) were plated on the various agar plates and evenly spread over the entire plate using a flame sterilized glass rod. The inoculated plates were incubated at 35°C for 48hrs. Discrete colonies from the culture plates were picked with sterile wire loop and inoculated onto freshly prepared MRS agar plates. The pure isolates were identified following a four-step analysis the steps employed are cultural examination, microscopic examination, biochemical reaction and sugar utilization test. In the present investigation, the five LAB isolates obtained from various fermented food samples were identified after morphological, biochemical and sugar fermentation tests as: Bacillus subtilis, Bacillus lichenforinis, L. plantarum, Enterobacter species and Streptococcus species. The lactic acid bacterial isolates (Bacillus subtilis, Bacillus lichenformis, L. plantarum, Enterobacter species and Streptococcus species) were tested for antibacterial activity against Escherichia coli and Staphylococcus aureus which served as test organisms The inhibitory effect demonstrated by the lactic acid bacterial isolates against these bacteria is an indication of possession of antibacterial activity. Various factors seemed to affect bacteriocin production as well as its activity. Maximum activity was noted at pH 2, and temperature 50°C. Bacteriocin production was strongly dependent on pH and temperature. The production of these bacteriocins was much higher at 50 °C than at 40°C, which suggested that the growth temperature also played an important role. Proximate Analysis of Ogiri Samples was carried out using the method described by Association of Official Analytical Chemist (AOAC). The result of the proximate analysis indicated that the dry matter content of the samples was high with a percentage value of (52.09%), followed by the moisture content of (38.02%), fat content of (28.57%), protein content of (12.22%), carbohydrate content of (11.7%), fibre content of (9.39%) and Ash content of (7.41%). This study concluded that the bacteriocin antibiotic produced by lactic acid bacterial isolates demonstrated inhibitory effects against bacterial indicator organisms.