Evaluation of Antibacterial Activity of Lactic Acid Bacteria Isolated from Kunun Zaki against Selected Bread Rope Spoilage Bacteria

In line with increasing demand by consumers for safe and minimally processed food products, biopreservation has been advocated over the traditional use of chemical additives in combating food spoilage. This study evaluated the antibacterial activity of four lactic acid bacteria (LAB) (Lactobacillus fermentum, Lactococcus lactis, Lactobacillus brevis and Lactobacillus plantarum) isolated from kunun-zaki against the bread rope spoilage bacteria, Bacillus subtilis and Bacillus cereus. Antibacterial activity was determined using the dual agar overlay method with subsequent measurement of zones of inhibition. Titrimetric methods were used to determine the abilities of the isolated LAB to produce antimicrobials including lactic acid, hydrogen peroxide and diacetyl. Lactobacillus fermentum brought about the highest inhibition zone (20 mm) against Bacillus cereus. The smallest zone of inhibition (6 mm) was recorded for L. plantarum against B. cereus. Whereas L. plantarum produced the highest amount of lactic acid (0.540 g/L), L. brevis produced the lowest lactic acid amount of 0.348 g/L. L. fermentum produced the highest amount of hydrogen peroxide (0.020 g/L) whereas L.brevis recorded the lowest hydrogen peroxide production of 0.010 g/L. L. lactis and L. fermentum had the highest and lowest values of 0.649 g/L and 0.219 g/L respectively for diacetyl production. Differences in the antibacterial activities and antimicrobials production by the LAB were statistically significant (P < .05). The findings show that the LAB isolates possessed antibacterial activity against the selected spoilage bacteria and as such could be exploited as potential biocontrol agents against the selected bread rope spoilage bacteria.