Abstract

Lactic acid bacteria are important organisms that have been used as starter cultures for the fermentation of food and food products. This study was aimed at evaluating the potentials of Lactic acid bacteria (LAB) isolated from ogi for development of starter culture and amylase production. Isolation of the LAB isolates was done on de Mann Rogosa Sharpe (MRS) agar using standard microbiological techniques. The isolates were evaluated for use as starter cultures by assaying for acidification, production of lactic acid and hydrogen peroxide. Amylase activity was determined by the spectrophotometric method employing starch as substrate and 3, 5 dinitrosalicyclic acid (DNS) as coupling reagent. The identification of Lactic acid bacteria isolates obtained from samples of ogi indicated that Lactobacillus fermentum, Lactobacillus rhamnosus, Lactobacillus fermentum and Lactobacillus plantarum were the main organisms involved in the fermentation of ogi. From the results obtained, it was evident that the quantity of lactic acid produced increased following a decline in pH as fermentation time increased. It was observed that L. plantarum produced the highest quantity of lactic acid (3.85 gL^-1) at 48 hrs compared to all other LAB species used in this work with a strain of L. fermentum having the lowest yield 2.65 gL^-1) after 48 hrs of incubation. The highest (1.24 g/l) concentration of hydrogen peroxide was produced by L. fermentum at 24 hrs of incubation. Increasing incubation resulted in a reduction in the quantity of hydrogen peroxide produced. Hydrogen peroxide produced by the LAB strains ranged between 0.46 to 1.24 g/l. The results of this study showed that amylase production increased with increase in incubation time linearly till the 96^th hours. Maximum amylase (3.47U/g) production was obtained at 96hrs. The study revealed that the strains isolated had an optimum pH of between 3.0 to 3.5 with a maximum enzyme activity of 4.28 U/g. Maximum enzyme production was obtained with maize bran as substrate recording 2.48 U/g after 96 hrs of incubation. The results of this study showed that L. plantarum and L. fermentum can be used as potential starter cultures in the production of ogi and cultivation of these isolates using a cheap substrate (maize bran) will result in increased amylase synthesis for several applications.