Selection of probiotic bacteria for use in permented milk product

Abstract

Isolation of probiotic lactic acid bacteria for use in fermented milk product was carried on infant faeces, pig intestine and chickens intestine. Three hundred and seventy-nine isolates were isolated from 11 of infant faeces, 13 of pig intestine, and 15 of chicken intestine. Based on their phenotypic characteristics, 216 isolates were belonged to Lactobacillus, 122 isolates were Enterococcus and the other 41 isolates were unidentified. Twenty-nine isolates were acid- and bile-resistant at pH 2.5 and 0.3% bile salt, respectively. The potentially probiotic isolates IF2-8, P2-10 and CK8-11 were selected from infant, pig and chicken, respectively. IF2-8 was the best acid-resistant isolate at survival rate 96.4% and could inhibit E. faecium, Y. enterocolitica and B. cereus. Based on their phenotypic characteristics and 16S rDNA sequence similarity, IF2-8, P2-10, and CK8-11 were closely related to L.gasseri, L. johnsonii, and L. salivarius with 99.91, 99.53and 99.91%, respectively. Furthermore the other strains P12-3, IF7-5, and IF8-1 were closely related to L. amylovorus, E. raffinosus, and E. faecalis with 99.53, 99.75 and 99.83%, respectively. Later, the three potential probiotic strains were used for fermented milk trial which divided into 3 sets, the first was inoculated with IF2-8, P2-10, and CK8-11 culture, while the second was inoculated with the mixed culture of each probiotic culture and S. thermophilus, and the last was the control that was inoculated with yoghurt starter bacteria, S. thermophilus and L. delbrueckii subsp. bulgaricus. These products were incubated at 42 C for 24 h and stored at 5 C for 3 weeks. Upon the completion of incubation, IF2-8 had greatest survival (73.0-88.4%) in both fermented milk used only probiotic and fermented milk used probiotic and S. thermophilus. Furthermore, fermented milk used IF2-8 mixed with S. thermophilus resulted increasing in viability of IF2-8 (2 log cycles) compared to fermented milk that used only IF2-8. For acid production, the control fermented milk, only IF2-8 product and IF2-8 mixed with S. thermophilus product were 1.54, 0.62 and 1.15%, respectively. Their viscosity were 488,256 and 601 cPs, respectively. Fermented milk used only IF2-8 was found that acid production and viscosity much lower than the control, whereas fermented milk mixed with S. thermophilus produced acid not different from the control. Therefore, this results indicated that IF2-8 should be applied along with S. thermophilus in fermented milk but it could not be used as starter culture alone in fermented milk.