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Öğe Characterization of Pediococcus acidilactici PFC69and Lactococcus lactis PFC77 Bacteriocins and TheirAntimicrobial Activities in Tarhana Fermentation(2020) KAYA, HALİL İBRAHİM; ŞİMŞEK, ÖMERTarhana is a traditional cereal product fermented by lactic acid bacteria (LAB) and yeast strains that has gained special interest recently as an infant nutrition. Tarhana contains wheat flour, yogurt, and various vegetables that might create a microbiological toxicological risk, especially for Bacillus cereus and Staphylococcus aureus. In this study, characterization of the metabolites responsible for antibacterial activity of Pediococcus acidilactici PFC69 and Lactococcus lactis PFC77 strains obtained from tarhana was performed, and antibacterial e ects were detected against B. cereus ATCC 11778 and S. aureus ATCC 29213 during the fermentation. A total of 12,800 AU/mL antibacterial activity was observed for the supernatants of the PFC69 and PFC77 strains that were found to be stable at high temperature and in low pH conditions and sensitive to proteases, suggesting the antimicrobial metabolite is a bacteriocin. These bacteriocins were further purified and their molecular sizes were determined as 4.5 and 3.5 kDa, respectively. Importantly, inoculation of PFC69 and PFC77 to tarhana dough significantly decreased B. cereus ATCC 11778 and S. aureus ATCC 29213 amounts from the fifth day of fermentation compared to the control dough samples. P. acidilactici PFC69 and L. lactis PFC77 strains were concluded as bioprotective cultures for tarhana and these strains were o ered for other cereal-based fermentations.Öğe A novel bacteriocin produced by Lactobacillus delbrueckii subsp. lactis with a specifically antimicrobial activity against Bacillus cereus(2017) KAYA, HALİL İBRAHİM; ŞİMŞEK, ÖMERBacteriocins are the ribosomal synthesized antimicrobial peptides used as natural preservatives against pathogens during food production process. The main problem of using bacteriocin and their producers is that these antimicrobials also inhibit the existing flora including non-starter lactic acid bacteria. The question is whether bacteriocins with narrow antimicrobial activity could be a solution? In this study, bacteriocins produced from lactic acid bacteria (LAB) having antimicrobial activity specifically on Bacillus cereus (BC) was isolated and characterized. To select the anti-BC bacteriocin LAB producer, a cocktail including of diverse B. cereus strains was used as indicators. The isolate Yo6B1 obtained from condensed yogurt showed antimicrobial activity against BC at both spot and well diffusion assays. This isolate and its bacteriocin-like metabolite did not inhibit any LAB tested, although it had antimicrobial activity against all BC strains (n=59) isolated from food samples. 16S rDNA sequence of Yo6B1 indicated that it was 99% homolog with the Lactobacillus delbrueckii subsp. lactis. The partial purified Yo6B1 was degraded with proteolytic enzymes including trypsine, α-chmotrypsine, pepsine and proteinase K proved that Yo6B1 was a bacteriocin although the genome of Lb. delbrueckii subsp. lactis did not contain any known bacteriocin production genes. MALDI-ToF analysis indicated that bacteriocin Yo6B1 has a small molecular size. As a conclusion, Lb. delbrueckii subsp. lactis produced a novel narrow spectrum bacteriocin, which has specifically antimicrobial activity against BC. This study also demonstrated that pathogen-specific bacteriocins could be used to eliminate pathogens in foods with no antibacterial effects against LAB microflora.Öğe A Natural Way of Food Preservation: Bacteriocins and applications(Springer International Publishing, 2019) KAYA HALİL İBRAHİM; ÖZEL BURCU; ŞİMŞEK ÖMERSince the consumers demand foods produced without additives, new friendly preservation strategies become significant in processing of foods. Bacteriocins are ribosomally synthesized peptides produced from many bacterial strains which are approved as natural due to being degraded by digestive enzymes. In Lactic acid bacteria (LAB), many strains have been identified as bacteriocin producers. In fact, nisin was approved by Food and Drug Administration (FDA) to be used as food additive in some foods. Lacticin and pediocin producers, Lactococcus lactis and Pediococcus acidilactici, respectively, have been used as protective cultures in food system. Bacteriocins produced by some LAB have shown wide antimicrobial activity against food related pathogens species such as Bacillus, Listeria, Staphylococcus and Clostridium. However, in recent years bacteriocins having specifically narrow-spectrum antimicrobial activity have been introduced. Bacteriocins are used either directly in food systems or by the addition of producer strains. In this way, it has been possible to prevent pathogenic microorganisms in various fermented food products. However, the effectiveness of the LAB bacteriocins may reduce due to their adsorption on to the hydrophobic surfaces and degradation with proteases. Therefore, the combinational usage of bacteriocins with other preservation methods, such as high hydrostatic pressure, pulse electrical field or essential oils, were reported successful at inhibiting pathogens including the Gram negatives. In the first part of the chapter, the general introduction to bacteriocins and new generation bacteriocins are discussed. In the second part, the applications of bacteriocins in different food systems have been explained and the combinational usage of bacteriocins together with different preservation methods have been exemplified.
