Lactic Acid and Probiotic Bacteria from Fermented and Probiotic Dairy Products

Lactic acid and probiotic bacteria were enumerated and isolated from commercially available yoghurt andprobiotic milk products. Lactobacillus delbrueckii ssp. bulgaricus were enumerated and isolated usingMRS agar incubated anaerobically at 37oC for 72 hrs. M17 agar was used for the enumeration andisolation of Streptococcus thermophilus incubated aerobically at 37oC for 48 hrs. MRS agar and modifiedMRS agar (MRS + L-cysteine + LiCl + Na propionate) were used for the enumeration and isolation ofprobiotic bacteria. Both were incubated anaerobically at 37oC for 72 hrs. Morphological, physiologicaland biochemical reactions were used to characterize the isolates.Str. thermophilus counts ranged from 2.6 x 1011 to 2.9 x 1020 CFU/g with Fruit Yoghurt (FY) having thehighest count and Yoghurt Natural (YN) with the lowest count. Highest Lactobacillus delbrueckii ssp.bulgaricus count was obtained in Duo Yoghurt (DY), 1.1 x 109 and lowest in Yoghurt Drink (YD), 8.0 x 107CFU/g. The highest probiotic bacterial count of 2.3 x 108 was obtained in Yakult (YK) and Neslac (Nes)showed the lowest, 1.6 x 102 CFU/g. The viable counts of all the products examined met the prescribedminimum viable count of 105 to 106CFU/g for the claimed health benefits for the consumer except forChamyto Plain (CP), Nes and Nan-2 (Nan).Morphological, physiological and biochemical characteristics showed that the following genera andspecies were present Pediococcus acidilactici (YN), P. pentosaceus (FY), Lactobacillus delbrueckiidelbrueckii and L. brevis in Non Fat High Calcium Yoghurt (NC), L. acidophilus and L. delbrueckiidelbrueckii (DY, YD), P. damnosus and P. pentosaceus in Chamyto Orange (CO), L. delbrueckii bulgaricus,L. acidophilus, and L. delbrueckii delbrueckii (CP), L. para. paracasei (YK) and Bifidobacterium ssp.(Nes and Nan).Of the 28 isolates characterized in this study, 15 were Lactobacillus (5 species), 5 werePediococcus (3 species), 6 were Bifidobacterium (species not identified), and 2 were Actinomyces israelii(1 species)