Gülden Başyiğit Kılıç

In-vitro microbial production of conjugated linoleic acid by probiotic L. plantarum strains: Utilization as a functional starter culture in sucuk fermentation

Twenty-three probiotic Lactobacillus plantarum strains were screened in-vitro to determine their ability to produce conjugated linoleic acid (CLA). L. plantarum AA1-2 and L. plantarum AB20-961 were identified as potential strains for CLA production. Optimum conditions for these strains to produce high levels of CLA were determined by evaluating the amount of added hydrolyzed sunflower oil (HSO) and initial pH levels in a nutrient medium. The highest CLA production was obtained in medium with pH6.0 and 2% HSO (P<0.05). Those strains were then used as starter culture in sucuk fermentation. Five sucuk treatments included a control (no starter culture), two sucuk groups with L. plantarum AA1-2 at the initial pH of 5.8 or 6.0 and two sucuk groups with L. plantarum AB20-961 at the initial pH of 5.8 or 6.0. Results indicate that L. plantarum AB20-961 produced higher amount of CLA in sucuk at initial pH of 5.8 and 6.0 levels during first 24h of fermentation compared with other groups. CLA isomer concentration decreased in all sucuk groups during the rest of the fermentation period (P<0.05) and remained quite stable during the storage. This study demonstrated that probiotic L. plantarum AB20-961 can be used in sucuk manufacturing without posing any quality problems.

Determining potential probiotic properties of human originated Lactobacillus plantarum strains

In this study, twenty Lactobacillus plantarum strains which were isolated from the fecal samples of humans were investigated in vitro for their characteristics as potential new probiotic strains. The L. plantarum strains were examined for resistance to gastric acidity in simulated gastric juice at pH 2.0, 2.5, 3.0, and 3.5. The growth of test cultures with different pH was monitored after 0, 10, 30, 60, 90, and 120 min of incubation using a spectrophotometer at 550 nm. At the same time, samples were serially diluted in sterile PBS, and counts of viable bacteria were determined by plate counts using MRS agar for each pH and time parameter. The strains were also examined for resistance to 0.4% phenol, production of H2O2, adhesion to Caco-2 cell line and antimicrobial activity. It was determined that the artificial gastric juice, even at pH 2.0, did not significantly change the viability of the cultures. Except L. plantarum AA1-2, all strains were detected at 8 ∼ 9 log10 CFU/g. It was found that all L. plantarum strains showed good resistance to 0.4% phenol, and only one strain (AC18-82) produced H2O2. Good adhesion of L. plantarum strains to Caco-2 cells was observed in this experiment. These selected strains also showed antimicrobial activity.

Microbiological, physicochemical properties and biogenic amine contents of the strained yoghurts from Turkish local markets

Thirty three strained yoghurt samples were collected from local open markets in different provinces of Turkey (Afyon [AF], Aydin [AY], Burdur [B], Isparta [I] and Mugla [M]). Physicochemical and microbiological properties, as well as biogenic amine content, were examined in each of the samples. The dry matter (17.90 to 26.44%), fat (5.51 to 10.44%), ash (0.65 to 1.48%), lactic acid (1.69 to 2.05 g l -1 ), salt (0.61 to 1.68%), pH (3.52 to 3.94), protein (5.73 to 8.57%) and syneresis (1.67 to 9.22%) of samples differed as indicated. The mean of the lactobacilli counts ranged from 6.63 to 8.35 Log 10 CFU g-1, lactococci ranged from 7.16 to 8.02 Log 10 CFU g -1 , while streptococci and propionic acid bacteria ranged from 6.71 to 7.27 and 5.60 to 8.38 Log 10 CFU g -1 , respectively. All the yoghurts were contaminated with fungi and coliforms at levels above the acceptable limits, indicating insufficient process hygiene and also raising concerns of consumer safety. Tryptamine is the only biogenic amine determined in all yoghurt samples. Cadaverine, putrescine, tyramine and b-phenylethylamine were not detected in any of the samples. Key words : Strained yoghurt, physicochemical properties, biogenic amine, tryptamine.