Growth parameters and sanitizer resistance of Raoultella ornithinolytica and Raoultella terrigena isolated from seafood processing plant

Abstract

This study examined the effects of pH, temperature, NaCl concentration and heat resistances of Raoultella spp. isolated from a seafood processing plant in Thailand. The ability to resist to cleaning and sanitizing agents were also investigated. The effect of growth medium (Tryptic Soy Broth) adjusted to various pHs (3, 4, 5, 6, 7, 8, 9, 10) revealed Raoultella ornithinolytica and R. terrigena were able to grow well at pH 6–9, slow growth at 4 and 10 but not at strong acidic pH 3. Growth at different temperature was done (4, 15, 20, 37, 40°C) and found optimum growth was ranged at 15–37°C. Sodium chloride concentrations test was at 1%, 1.5%, 2.5%, 3.5%, 4.5%, 5.5% and 6.5% revealed the optimal growth at 1–4.5% NaCl. D-values of both species gave similar result as 0.66–0.79 min at 57°C, with Z-value 4.2–4.5°C. When cell suspension and biofilm were exposed to cleaning agent (sodium hydroxide, lauryl dimethylamine oxide, and sodium hypochlorite), and three sanitizers, namely, sodium hypochlorite (NaClO), hydrogen peroxide (H₂O₂), and ozonated water. NaClO was able to eliminate single biofilm of Raoultella spp. at 50 ppm in 5 min while ozone had less efficacy to kill biofilm cells. H₂O₂ at 1% and 2% succeeded to eliminate biofilm. This finding properties of Raoultella spp. will be useful for designing strategies to prevent and control contamination these species regarding seafood plant sanitation.

Keywords:

• sanitizing
• food safety
• Raoultella spp
• cleaning
• thermal resistance

PUBLIC INTEREST STATEMENT

This study focus on Raoultella spp. (R. ornithinolytica and R. terrigena) because of the capacity to be a major spoilage bacteria in seafood products. These species has also been mentioned as the potential of histamine producing bacteria. Currently, some studies have been reported on the growth characteristics of R. terrrigena, but only a few mentioned the growth factors pertaining to R. ornithinolytica. The food industry realized that adhesion and colonization of bacteria may cause problems, and an important source of bacterial contamination. Therefore, this study investigated the growth parameters of the two species of Raoultella isolated from seafood processing environments; the cleaning of biofilm produced under stress conditions simulated to seafood processing area was also examined

This article reveals the growth ability, thermal resistance of R. ornithinolytica and R. terrrigena. Expectation that these information may assist to the control strategies to prevent and control the growth of these bacteria, and to enhance the safety of seafood products.

Competing Interests

The authors declared that they have no competing interests.

Acknowledgements

This work was supported by the Office of the Higher Education Commission and the graduate scholarship from the National Research Council of Thailand (NRCT). The authors thank Nguyen Thi Quynh Anh for valuable assistance and Department of Food Science and Technology, Kasetsart University for providing instruments.

Additional information

Funding

This work was supported by the Office of the Higher Education Commission and the graduate scholarship from the National Research Council of Thailand (NRCT).

Notes on contributors

Adisara Tantasuttikul

Adisara Tantasuttikul is a Ph.D. student in Food Science and Technology at Department of Food Science and Technology, Kasetsart University, Bangkok, Thailand. Her interest is quality and safety of seafood and hygienic practices in seafood process.

Warapa Mahakarnchanakul

Warapa Mahakarnchanakul is an assistant professor in the Department of Food Science and Technology at Kasetsart University, Bangkok, Thailand. Her Ph.D. is in Food Science from The University of Georgia, USA. Her currently research is the cleaning and sanitizing of fresh produce and seafood. Microbial stress response in food is also her research of interest.