Probiotic properties of lactic acid bacteria isolated from dairy products and their potential for use as a starter culture

In this study, lactic acid bacteria (LAB) were isolated from raw milk and yoghurts produced by spontaneous fermentation using these milks, and the starter culture and probiotic potentials of these LAB isolates were investigated. A total of 116 bacteria were isolated in isolation studies conducted using MRS agar. 22 of these isolates have been accepted as LAB because they are gram-positive (+), catalase-negative (-), immobile and spore-free. Starter culture and probiotic properties of the isolates that did not carry virulence factors were determined. Of the 22 isolates of the LAB, 4 were found to be β-hemolytic (4/22), 5 (5/22) were found to be enterococci and were not included in subsequent studies. The fact that 4 of the remaining 13 isolates (isolates 6, 9, 10 and 12) remained alive at low pH (pH= 1, 2, 3 and 4), bile salty environment (0.3% and 0.6%) and artificial gastric fluid (NaCl+pepsin, pH=2 and 3) showed that they had probiotic potentials. The acidification times of UHT milk of the same isolates (24 hours at 42, 43, 44 and 45 ° C) were determined. At all temperature degrees tested, the first 3 isolates with the highest ability to acidify milk, respectively; he has been 15, 13, 12, 16 and 23. The optimal temperature for acidification of UHT milk isolates was determined as 42oC. Then, 2 isolates (Nos. 15 and 23) that acidify milk in a short time and 1 isolate with probiotic potential (Nos. 12) were selected from them in different combinations (23+15, 23+12, 15+12, 23+15+12) starter culture preparations were prepared and yogurt (at 42oC, 24 hours) was obtained using UHT milk. As a result, yoghurts with similar properties to traditional yoghurts have been obtained with combinations of 23, 15, 12. The most prominent combination in terms of aroma is the combinations containing isolate number 15. The findings obtained from the study show that the domestic isolates involved in spontaneous yogurt fermentation have the potential to be used in yogurt production, but also showed that they have probiotic properties.