Author

Qian Shen

Advisor

Nannapaneni, Ramakrishna

Committee Member

Kim, Taejo

Committee Member

Schilling, M. Wes

Date of Degree

1-1-2013

Document Type

Graduate Thesis - Open Access

Degree Name

Master of Science

College

College of Agriculture and Life Sciences

Department

Department of Food Science, Nutrition and Health Promotion

Abstract

Acid-stress adaptation in Listeria monocytogenes (Lm) serotype 4b and 1/2a occurred when cells were pre-exposed to pH 5.0 tryptic soy broth supplemented with yeast extract (TSB-YE) at 22°C or 37°C but not at 4°C. Prolonged time, varied sublethal acid pH, substitute of acidulants and addition of sodium chloride during 4°C mild acid pre-exposure still did not induce acid-stress adaptation in Lm. This finding was also validated using an acidic cheese, similar to what has seen for Gram-negative bacteria E. coli and Salmonella. Further investigation revealed that major cold shock protein in Lm CspL was not responsible for repressed acid-stress adaptation at 4°C. A bead beating treatment prior to mild acid pre-exposure at 4°C partially induced acid-stress adaptation after pre-exposure in 4°C to mild acid stress. Our data suggests that cold processing or cold storage temperature can lower the possibility of activating acid-stress adaptation in Lm.

URI

https://hdl.handle.net/11668/19874

Comments

cold stress||temperature||acid-stress adaptation||Listeria monocytogenes

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