tailieunhanh - The effect of acid adaptation conditions on acid tolerance response of Escherichia coli O157: H7

The results indicated that exposure to acidic environments (pH ) for a short time increased acid tolerance of E. coli O157: H7. Acid shocked cells of E. coli O157: H7 may be considered in fermented foods, fruit juices and for acid spray process in the meat industry. | Turk J Biol 29 (2005) 197-202 © TÜB‹TAK The Effect of Acid Adaptation Conditions on Acid Tolerance Response of Escherichia coli O157: H7 Halil TOSUN Department of Food Engineering, Faculty of Engineering, Celal Bayar University, Manisa - TURKEY fiahika AKTU⁄ GÖNÜL Department of Food Engineering, Faculty of Engineering, Ege University, ‹zmir - TURKEY Received: Abstract: This study examined the effects of acid shock and acid adaptation on acid tolerance of E. coli O157: H7 932 strain. E. coli O157: H7 were exposed to acid at pH , or for acid adaptation or acid shock in tryptic soy broth (acidified with 6 N HCI). Acid shocked cells were incubated for 1, 2, 3 or 4 h while acid adapted cells were incubated for 18 h at 37°C and then acid tolerance of acid shocked and acid adapted cells were determined by exposing to acid challenge of pH or in tryptic soy broth. Acid shocked, acid adapted and control cells were incubated at 37°C and survival of the cells at 0, 2, 4, 6, 7, 24 and 48 h was determined. Acid shock increased acid tolerance of E. coli O157: H7 at pH . However, acid tolerance was not induced in acid adapted cells at either pH or . Acid shocked cells exposed to acid at pH for 2 h had the highest acid tolerance (P < ). The results indicated that exposure to acidic environments (pH ) for a short time increased acid tolerance of E. coli O157: H7. Acid shocked cells of E. coli O157: H7 may be considered in fermented foods, fruit juices and for acid spray process in the meat industry. Key Words: E. coli O157: H7, Acid shock, Acid adaptation, Adaptation time Aside Adaptasyon Koflullar›n›n Escherichia coli O157: H7’nin Aside Tolerans Kazanmas› Üzerindeki Etkisi Özet: Bu çal›flmada, asit floku veya aside adaptasyon iflleminin E. coli O157: H7 932 suflunun aside tolerans kazanmas› üzerindeki etkileri incelenmifltir. Duraklama faz› hücreleri pH’s› 6 N HCI ile , ve ’ e ayarlanm›fl tryptic soy broth .