ABSTRACT

Lactic Acid Bacteria (LAB) are the most widespread group of bacteria that is used in fermented foods. They are natural inhabitants of the human gastric intestine, and can be applied in different fermented products and probiotic foods. This study was to evaluate lactic acid bacteria response to heat stress of which two (2) samples of Ogiri were selected for the isolation and evaluation of lactic acid bacteria and its response to heat stress. From this study three (3) lactic acid bacteria were isolated and identified from the Ogiri sample using colonial morpholOgiries, Gram staining, motility and biochemical tests. These revealed the major lactic acid bacteria to be Lactobacillus plantarium, Lactobacillus helveticus, and Lactobacillus brevis. In this present study, the different temperatures at which the lactic acid bacteria species were treated for 30 minutes before inoculation and incubation at 37oC revealed that the total bacterial counts for L. planetarium had its maximum at 50oC (1.37x105) but was declined below and above 50°C temperature. This revealed that L. planetarium was able to survive heat stress at a maximum temperature of 50°C. In addition it was also revealed in this study that Lactobacillus helveticus and Lactobacillus brevis remained cultivable at 55oC (1.41x105) and 40oC (1.99x105) respectively, which demonstrates that bacteria are able to withstand such adverse environmental conditions. Bacteria activate mechanisms allowing them to adapt to new conditions, which can influence the viability and technolOgirical properties. Lactic Acid Bacteria can be used as live cells at optimum temperature since they have a Generally Recognized as Safe status during the production of bacteriocins. Further research needs to be done to find out more on the various temperatures at which lactic acid bacteria can survive