Lactic Acid and Probiotic Bacteria from Fermented and Probiotic Dairy Products

Lactic acid and probiotic bacteria were enumerated and isolated from commercially available yoghurt and probiotic milk products. Lactobacillus delbrueckii ssp. bulgaricus were enumerated and isolated using MRS agar incubated anaerobically at 37 degrees C for 72 hrs. M17 agar was used for the enumeration and isolation of Streptococcus thermophilus incubated aerobically at 37 degrees C for 48 hrs. MRS agar and modified MRS agar (MRS + L-cysteine + LiCl + Na propionate) were used for the enumeration and isolation of probiotic bacteria. Both were incubated anaerobically at 37 degrees C for 72 hrs. Morphological, physiological and biochemical reactions were used to characterize the isolates. Str. thermophilus counts ranged from 2.6 x 10(11) to 2.9 x 10(20) CFU/g with Fruit Yoghurt (FY) having the highest count and Yoghurt Natural (YN) with the lowest count. Highest Lactobacillus delbrueckii ssp. bulgaricus count was obtained in Duo Yoghurt (DY), 1.1 x 10(9) and lowest in Yoghurt Drink (YD), 8.0 x 10(7) CFU/g. The highest probiotic bacterial count of 2.3 x 10(8) was obtained in Yakult (YK) and Neslac (Nes) showed the lowest, 1.6 x 10(2) CFU/g. The viable counts of all the products examined met the prescribed minimum viable count of 105 to 10(6)CFU/g for the claimed health benefits for the consumer except for Chamyto Plain (CP), Nes and Nan-2 (Nan). Morphological, physiological and biochemical characteristics showed that the following genera and species were present Pediococcus acidilactici (YN), P. pentosaceus (FY), Lactobacillus delbrueckii delbrueckii and L. brevis in Non Fat High Calcium Yoghurt (NC), L. acidophilus and L. delbrueckii delbrueckii (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 were Pediococcus (3 species), 6 were Bifidobacterium (species not identified), and 2 were Actinomyces israelii (1 species).