Homofermentative lactic acid bacteria of a traditional cheese, Comlek peyniri from Cappadocia region.
ABSTRACT Comlek peyniri is a typical artisanal cheese in Central Anatolia. This type of cheese was made by using the indigenous lactic acid bacteria (LAB) flora of cow or ewes' milk. Majority of the samples were taken from fresh cheese because the aim was to isolate homofermentative LAB. Initially 661 microbial isolates were obtained from 17 cheese samples. Only 107 were found to be homofermentative LAB. These isolates were selected and identified by using both phenotypic and molecular methods. Phenotypic identification included curd formation from skim milk, catalase test, Gram staining and light microscopy, growth at different temperatures and salt concentrations, arginine hydrolysis, gas production from glucose, and carbohydrate fermentation. Molecular identification was based on the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of the 16S rRNA gene-ITS (internally transcribed spacer) region. By combining the phenotypic and molecular identification results, isolates belonging to each of the following genera were determined at species or subspecies level: 54 Lactococcus lactis subsp. lactis, 21 Enterococcus faecium, 3 Ec. faecalis, 2 Ec. durans, 10 Ec. sp., 15 Lactobacillus paracasei subsp. paracasei, and 2 Lb. casei strains. Technological characterisation was also performed by culturing each of the strains in UHT skim milk, and by monitoring pH change and lactic acid production at certain time intervals through the 24 h incubation. Results of the technological characterisation indicated that 33% of the isolates (35 strains) were capable of lowering the pH of UHT milk below 5.3 after 6 h incubation at 30 degrees C. Thirty four of these strains were Lc. lactis subsp. lactis, and only one was an Ec. faecium strain.
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ABSTRACT: The objective of the present study was to investigate the influence of container material (plastic or goat-skin bag) on the growth of lactic acid bacteria in Tulum cheese during 9months of ripening. The lactic acid bacteria in Tulum cheeses were periodically counted on MRS and M17 agars throughout ripening. Results showed that the highest counts of lactic acid bacteria on MRS or M17 were observed at the beginning of ripening and their counts decreased during later stages of ripening. The cheese samples ripened in plastic bags exhibited higher numbers of LAB on MRS and M-17 agars than those ripened in goat-skin bags. A total of 112 strains of lactic acid bacteria were isolated from Tulum cheeses ripened in plastic or goat-skin bags during ripening. The lactic acid bacteria present in the cheese were classified by Microbial Identification System (MIS) based on a comparison of the fatty acid methyl ester profiles. Different species including Enteroccocus, Lactobacillus, Streptococcus, Lactococcus and Pediococcus genera were found in unripened cheese. As ripening proceeded, the species Streptococcus and Lactococcus disappeared and the percentages of the species Enterococcus was unchanged in both containers. There were slight differences between the cheeses ripened in plastic or goat-skin bags in terms of the profiles of lactic acid bacteria isolated. Some species including L.brevis, L.mesenteroides subsp. dextranicum, P.damnosus and E.mundtii were isolated only in the cheeses ripened in plastic bags; however, L.coryniformis and L.malafermentans were isolated only in the cheeses ripened in goat-skin bags at 6 or 9months of ripening. Also the numbers of E.faecalis isolates were higher in the cheeses ripened in plastic containers than cheeses ripened goat-skin bags at the 6 or 9months of ripening. The results showed that Lactobacillus and Enterococcus were the predominant species in matured Tulum cheeses in both ripening containers. It seemed possible to produce Tulum cheese with similar characteristics from both the containers used.World Journal of Microbiology and Biotechnology 04/2012; 24(3):293-299. · 1.26 Impact Factor
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ABSTRACT: The use of commercial starter cultures in fresh cheese production from pasteurized milk results in the loss of typical characteristics of artisan fresh cheese due to the replacement of complex native microbiota with a defined starter culture. Hence, the aim of this research is to isolate and characterize dominant lactic acid bacteria (LAB) in artisan fresh cheese and to evaluate their capacity as autochthonous starter cultures for fresh cheese production. Fifteen most prevalent Gram-positive, catalase-negative and asporogenous bacterial strains were selected for a more detailed characterization. Eleven lactic acid bacterial strains were determined to be homofermentative cocci and four heterofermentative lactobacilli. Further phenotypic and genotypic analyses revealed that those were two different LAB strains with high acidifying and proteolytic activity, identified as Lactobacillus fermentum A8 and Enterococcus faecium A7. These two autochthonous strains, alone or in combination with commercial starter, were used to produce different types of fresh cheese, which were evaluated by a panel. Conventional culturing, isolation, identification and PCR-denaturing gradient gel electrophoresis (PCR-DGGE) procedures, applied to the total fresh cheese DNA extracts, were employed to define and monitor the viability of the introduced LAB strains and their effect on the final product characteristics. Production of fresh cheese using a combination of commercial starter culture and selected autochthonous strains resulted in improved sensorial properties, which were more similar to the ones of spontaneously fermented fresh cheese than to those of cheese produced with only starter culture or selected strains. After 10 days of storage, that cheese retained the best sensorial properties in comparison with all other types of cheese. The presence of inoculated autochthonous and starter cultures and their identification was demonstrated by DGGE analysis. The obtained results indicate that autochthonous strains have a strong potential to enrich the flavour of industrially produced fresh type cheese under controlled conditionsFood Technology and Biotechnology 10/2012; 50(2):141. · 0.98 Impact Factor
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ABSTRACT: The ability of lactic acid bacteria (LAB) cultures to preserve goat meat at 30°C was evaluated in the present study. Strains of Pediococcus pentosaceus GOAT 01 and Lactobacillus plantarum GOAT 012, individually and in combination, were applied as starters on sliced meat samples at 6 log cfu/g and stored for 7days at 30°C to simulate ambient temperature in Nigeria. They were evaluated for microbiological profile during storage. Reduction in bacterial counts was recorded for enterobacteriaceae, Staphylococcus, yeasts and moulds in starter culture inoculated samples (SCIS), whereas an increase occurred in uninoculated control samples (UCS). In challenge experimental trials, two different sets of meat were inoculated individually with 6 log cfu/g each of pathogenic organisms, Listeria monocytogenes and Salmonella Typhimurium. The inoculated pathogens were monitored during storage to assess the influence of starter cultures on them. Approximately 1 log reduction was recorded in the viable count of L. monocytogenes on day 1, while counts were below detection limit (<2 log) on day 2 in meat samples inoculated with P. pentosaceus alone and in combination with L. plantarum. Counts of Salmonella Typhimurium showed about 2 log reduction in SCIS, inoculated with P. pentosaceus alone and in combination with L. plantarum, on day 2 while an increase by 4 logs was observed in UCS. Our findings suggest that the protective effect of the LAB strains could be exploited in shelf life extension and control of foodborne pathogens in goat meat. If the starter strains could be improved upon, their potential as biopreservatives may be engaged in the preservation of the meat in Nigeria, where storage systems have been very inadequate. KeywordsLactic acid bacteria–Foodborne pathogens–Protective effect–Biopreservatives–Storage systemsFood and Bioprocess Technology 04/2012; 4(2):312-319. · 4.12 Impact Factor