Ahmet Hilmi Çon

Determination of microbiological contamination sources during ice cream production in Denizli, Turkey

Ice cream is a food commodity consumed widely during summer. The aim of this research is to determine the microbiological contamination sources during ice cream production. The samples were collected from four different pastry shops in Denizli area in Turkey. Samples were taken for microbial analyses from six points (premix, fresh ice cream, sold ice cream, ice cream cabinet, firming dish, scoop water and the hands of factory and sales department personnel). The results showed that premix had low levels of coliforms, Staphylococcus aureus, total aerobic mesophilic bacteria (TAMB) and yeast and mould. The levels of these microorganisms were higher in the fresh ice cream than their corresponding premixes. Moreover, sold ice cream had the highest levels of all microorganism groups. The samples taken from ice cream cabinet and firming dishes contained low levels of TAMB and yeast-mould but no coliform, faecal coliform or S. aureus. On the contrary, high levels of coliforms, faecal coliform and S. aureus, TAMB and yeast-mould were found in the samples collected from factory/sales department personnel hands and scoop water. Overall results showed that cooling method, personnel hands and scoop water were the main sources of the microbial contamination of ice cream produced and sold in pastry shops.

Production of bacteriocin-like metabolites by lactic acid cultures isolated from sucuk samples

A total of 51 sucuk samples, obtained from different regions of Turkey, were examined for lactic acid bacteria (LAB) strains producing putative bacteriocin-like metabolites. For detection of antagonistic activity, agar spot and well diffusion assay tests were used. Lactobacillus sake Lb790, Listeria monocytogenes Li6, Staphylococcus aureus St44 and Escherichia coli NRRL B-3704 were used as indicator organisms. Strains having antimicrobial activity were also tested against Clostridium perfringens 4TTK, Clostridium botulinum type A. 7948, Bacillus cereus NRRL B-3711, Micrococcus luteus NRRL B-4376 and Yersinia enterocolitica type 103. 57 of 424 isolates from sucuk samples were putative producers of bacteriocin-like metabolistes and were identified as the following: 19 Lactobacillus plantarum, 4 L. curvatus, 4 Pediococcus pentosaceus, 3 P. acidilactici, 2 L. pentosus, 2 L. sake, 1 L. delbrueckii, 1 L. rhamnosus and 21 unidentified Lactobacillus spp. P. pentosaceus 416, P. acidilactici 413, 419 and 446, L. curvatus 348, L. plantarum 452 and 495, and Lactobacillus spp. 411 strains have the best potential for use as sucuk starter cultures.

Antagonistic effect on Listeria monocytogenes and L. innocua of a bacteriocin-like metabolite produced by lactic acid bacteria isolated from sucuk

Two Lactobacilli and four Pediococci strains producing bacteriocin-like metabolities isolated from sucuk were tested with agar spot tests and well diffusion assays for their inhibitory activity against 16 Listeria strains, also isolated from sucuk. The production of organic acids and hydrogen peroxide limited, L. sake Lb 706 (used as a bacteriocin producer strain) and the isolated lactic acid bacteria (LAB) showed inhibitory activity against all of the Listeria strains, while L. sake Lb 706-A (used as a bacteriocin non-producer mutant) had the same effects against only two Listeria monocytogenes strains (51, 52) in agar spot tests. In the well diffusion assays, while L sake Lb 706 and four Pediococci isolates (413, 416, 419, 446) exhibited inhibitory activity against all of the Listeria strains tested, L. sake Lb 706-A and two of the Lactobacilli isolates (77, 116) showed no effect on the Listeria strains tested.

Technological and probiotic characteristics of Lactobacillus plantarum strains isolated from traditionally produced fermented vegetables

The technological and probiotic characteristics of a number of Lactobacillus plantarum strains (previously isolated and identified from traditionally produced fermented vegetables) were compared, with the aim of identifying potential starter cultures to be used for the fermentation of vegetables. The L. plantarum strains were differentiated by their plasmid profiles; 12 separate strains with different plasmid profiles were examined. Other than survival in different concentrations of NaCl, the technological characteristics of all the strains examined were similar. However, strain-dependent variations in probiotic features were observed, with low pH in particular found to be a restrictive condition for all strains. The results indicated that, among the tested strains, L. plantarum 3 and 22 had good technological properties whereas L. plantarum 66 was significantly efficient in terms of probiotic features. Overall, L. plantarum 22 was found to be the most appropriate strain due to its combination of technological and probiotic properties.

Some characteristics of lactic acid bacteria present in commercial sucuk samples

A total of 10 sucuk samples, obtained from Denizli, Turkey were analysed for some physical, chemical and microbiological characteristics. In addition, lactic acid bacteria (LAB) strains producing bacteriocin-like metabolites were isolated and identified. The production of some typical metabolites of the cultures isolated was investigated. At the end of the research, the average values of the pH, water and fat content were 5.1, and 37.2% and 30.5%, respectively. Microbiological analyses results were determined: average 8.34 log CFU/g TAMB, 8.91 log CFU/g LAB (at the MRS agar) and average 8.25 log CFU/g LAB (at the Ellikers lactic agar). The average counts of yeast-mould, coliform and Enterobacteriaceae were found to be 5.0 log CFU/g, 3.28 log CFU/g and 3.27 log CFU/g, respectively. In this study, counts of yeast-mould in the two samples, coliform counts in the five samples, and Enterobacteriaceae counts in the three samples were < 1.0 log CFU/g. A total of 6 of 100 LAB isolates obtained from the sucuk samples were found as a strain producing bacteriocin-like metabolites. These 6 strains were identified as follows; 3 strains Lactobacillus plantarum and 3 strains Pediococcus pentosaceus. According to the findings, these strains have the potential to be used as a sucuk starter culture. Additionally, acid and flavour compounds, other undesirable metabolite-producing activities of the strains, were determined in the model system. From these results it was concluded, after the determination of the toxicological properties, that the 4 strains of LAB identified (L. plantarum 13 P. pentosaceus 15 P. pentosaceus 74 and P. pentosaceus 75) would be useful as the starter and protective culture in the processing of the sucuk and similar fermented products.

Influence of growth conditions on the nisin production of bioengineered Lactococcus lactis strains

Nisin production of three bioengineered strains, (LAC338, LAC339 and LAC340) with immunity (nisFEG) and/or regulation (nisRK) genes of nisin biosynthesis on plasmids in the Lactococcus lactis LL27 nisin producer, was evaluated under pH-controlled and pH-uncontrolled batch fermentations. Optimization studies showed that fructose and yeast extract yielded the highest nisin activity. The strains LAC338, LAC339, and LAC340 produced 24, 45, and 44% more nisin, respectively, than wild-type L. lactis LL27 after 12-h incubation. However, sharp decreases in the yield of nisin were observed at the late phase of fermentation with LAC339 and LL27 in contrast to LAC340 and LAC338 strains for which the high level of nisin could be maintained longer. Obviously, increasing the copy number of the regulation genes together with immunity genes in the nisin producers retarded the loss of nisin in the late phase of the fermentation.

Fourier transform infrared spectral evaluation for the differentiation of clinically relevant Trichophyton species.

Routine mold identification methods have been established to provide actual data to facilitate reliable diagnoses in clinical laboratories, as well as the management of infection and health practice planning, particularly for dermatophytes. Some species of the Trichophyton genera, particularly T. rubrum and T. mentagrophytes complexes, exhibit more complexity in species recognition. In this study, the intriguing technique of Fourier-transform infrared (FT-IR) spectroscopy is evaluated for species recognition of Trichophyton spp. A total of 32 reference isolates, belonging to T. mentagrophytes (n=7), T. rubrum (n=21) complexes and Arthroderma spp. (n=4), were included in the study. Numerous spectral window FTIR spectroscopy data were analyzed by principal component analysis and hierarchical clustering was performed. There were not any spectral ranges presenting clusters at the main Trichophyton species (e.g. T. rubrum, T. mentagrophytes and Arthroderma spp.). Notably, only T. violaceum (including T. yaoundei and T. soudanense) was clustered in several ranges. In intra-species evaluation, T. erinacei, belonging to the T. mentagrophytes complex, was distinguishable by FT-IR spectroscopy with different spectral range calculations. We suggested that further research with several reference and clinical isolates of Trichophyton species will be crucial to accurately identify intra-species of T. rubrum and T. mentagrophytes complexes.

Immobilization of nisin producer Lactococcus lactis strains to chitin with surface-displayed chitin-binding domain

In this study, nisin producer Lactococcus lactis strains displaying cell surface chitin-binding domain (ChBD) and capable of immobilizing to chitin flakes were constructed. To obtain ChBD-based cell immobilization, Usp45 signal sequence with ChBD of chitinase A1 enzyme from Bacillus circulans was fused with different lengths of PrtP (153, 344, and 800 aa) or AcmA (242 aa) anchors derived from L. lactis. According to the whole cell ELISA analysis, ChBD was successfully expressed on the surface of L. lactis cells. Scanning electron microscope observations supported the conclusion of the binding analysis that L. lactis cells expressing the ChBD with long PrtP anchor (800 aa) did bind to chitin surfaces more efficiently than cells with the other ChBD anchors. The attained binding affinity of nisin producers for chitin flakes retained them in the fermentation during medium changes and enabled storage for sequential productions. Initial nisin production was stably maintained with many cycles. These results demonstrate that an efficient immobilization of L. lactis cells to chitin is possible for industrial scale repeated cycle or continuous nisin fermentation.

Diversity and Stability of Yeast Species During the Fermentation of Tarhana

Tarhana is a traditional cereal-based fermented food produced with a mixture of yoghurt and flour. The main microbiota in the fermentation of tarhana is yeast, together with lactic acid bacteria. In this study, the yeast microbiota of home-made tarhana (HMT) and plant-type tarhana (PTT) dough samples was evaluated and compared during fermentation. Culture-dependent LSU and ITS-5.8S rDNA sequence analysis of yeast isolates collected during the tarhana dough fermentation clarified 45 selected isolates representing different clusters. These yeast isolates displayed high homologywith species Pichia kudriavzevii (11), Candida glabrata (11), Candida humilis (10), Saccharomyces cerevisiae (7), Kluyveromyces marxianus (4), Kazachstania servazzi (1), and Kazachstania unispora (1). Additionally, both culture-dependent and PCR-Denaturated Gradient Gel Electrophoresis (PCR-DGGE) analyses showed that S. cerevisiae, P. kudriavzevii and K. marxianus were abundant in the fermentation of HMT dough samples whereas P. kudriavzevii, C. humilis, and C. glabrata dominated the PTT dough samples. It was concluded that tarhana fermentation was accomplished with the presence of a wide variety of yeast species that mainly included P. kudriavzevii in both HMT and PTT dough samples.

Kombucha and Health

Kombucha is a fermented drink produced by fermentation of sweetened black and/or green tea with kombucha culture, it is known to have health benefits. The microflora of this fermented beverage mostly consists of AAB (acetic acid bacteria) and yeasts. Depending on its origin, LAB (lactic acid bacteria) sometimes will also be able to be found in the microflora. The production of kombucha and formation of its beneficial components are the result of the metabolic activities of this microflora. This fermented tea has been produced and consumed in the Far East for hundreds of years as a tradition; it is used as an adjunctive treatment for certain diseases. The interest in this tea has increased recently, and kombucha has spread worldwide. Its microflora diversity and metabolites are becoming important subjects of scientific studies. Although there are a few companies in Turkey that manufacture and market kombucha, there is no comprehensive scientific study on this subject. The liquid portion of kombucha is claimed to have various medicinal effects on human health. Recent studies have suggested that kombucha tea prevents paracetamol induced hepatotoxicity and chromate induced oxidative stress in albino rats. As kombucha tea is rich in compounds known to be strong antioxidants, it is expected to ameliorate liver damage. This beneficial effects of kombucha tea are attributed to the presence of tea polyphenols, gluconic acid, glucuronic acid, lactic acid, vitamins, amino acids, antibiotics and a variety of micronutrients produced during fermentation. The functional character of the kombucha should be investigated by a larger number of scientific studies. Co-use or self-use with various foods of this tea should be widespread.