Abstract
Tarhana 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 effects 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 offered for other cereal-based fermentations.
Highlights
Traditional fermented foods are a valuable resource for providing cheap, practical, and useful foods in the modern world
The antimicrobial activity was detected in supernatants of P. acidilactici PFC69 in the well diffusion assay except against Gram-negative rods and methicillin-resistant S. aureus (MRSA) (Table 1)
All the other enzymes did not have any effect on the antimicrobial activity of Bacteriocin-Like Substances (BLS) of P. acidilactici PFC69 and L. lactis PFC77. These results show that P. acidilactici PFC69 and L. lactis PFC77 produced bacteriocins with characteristics such as heat stability, proteolytic sensitivity, and solubility in acidic conditions
Summary
Traditional fermented foods are a valuable resource for providing cheap, practical, and useful foods in the modern world. Tarhana is a traditional fermented product obtained by the fermentation process of a dough prepared with wheat flour, yogurt, yeast, and various vegetables and spices (tomato, red pepper, onion, peppermint, salt) that is subjected to drying and grinding. This product is mainly produced and consumed as instant soup in Anatolia, but similar products have been produced in Greece, Hungary, and Egypt with different names [1]. Tarhana dough has a complex fermentation microbiota where yeast is found together with lactic acid bacteria (LAB). Even though the microbial diversity is high at the beginning of fermentation, acid-tolerant yeasts form the dominant flora with LAB in later flora [3,4,5]
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