ABSTRACT

The probiotic potentials oflactic acid bacteria species isolated from various food sources (nono, ugba, ogiri, kunun-zaki and ogi) were studied. Biochemical tests and mol G+C content were employed to ascertain the identity of the isolated strains. The predominant species among the isolated strains were Lactobacillus bulgaricus, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus brevis, Streptococcus thermophilus Leuconostoc mesenteroides and Pediococcus cerevisiae. The probiotic properties assessed were bile resistance, acid tolerance and ethanol tolerance. In vitro results obtained showed that three strains Lactobacillus bulgaricus, Lactobacillusplantarum and Streptococcus thermophilus were able to meet the basic requirements for probiotic functions such as tolerance to pH 3, growth in 0.5%(v/v) bile salt and ethanol at 5%(v/v). The isolates had low hydrophobicity property, ability to degrade raffinose and stachyose and coagulation of milk. The isolates also showed amylase activity. They producfed bacteriocins that inhibited the growth of S. aureus, E. coli and B. cereus. The mean lactic acid and hydrogen peroxide were 4.78±0.31 and 1.72±0.34g/100ml respectively. Lactobacillus bulgaricus and Lactobacillus plantarum were selected for the fermentation of vegetable substrates-carrot, cucumber and tomatoes and cereals-rice and maize for the purpose of studying the suitability ofthese raw materials for probiotic juice production. The fermentations were carried out at 30°C for 72h. The lactic acid bacteria had viability counts of 109 during storage at 4°C. The minimum pH attained during fermentation of samples was 3.9. The metals found in the fermented samples were calcium, magnesium, potassium, phosphorus and vitamin B complex was found in high concentrations. The best iron solubility was obtained from carrot juice which had value of 1.25±0.01. The highest reducing sugar concentration was found in rice 230±0.3mg/dl. The best bacteriocin preservative effect of 90% was observed in maize. The inoculums size of the lactic acid bacteria used for fermentation affected the final pH and reducing sugar concentrations ofthe samples. Rice gave the maximum alcohol concentration of 1.5% at 72h offermentation and the highest change in temperature of 30.5°C was observed in carrot juice. The fermented samples were subjected to sensory evaluation; carrot juice gave the best result on a 6 point hedonic scale. The lactic acid bacteria showed probiotic potentials in the juices sampled.