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Occurrence and Detection of Thermoanaerobacterium and Thermoanaerobacter in Canned Food

Christian Dotzauer, Matthias A. Ehrmann* and Rudi F. Vogel


Lehrstuhl für Technische Mikrobiologie, Technische Universität München, Weihenstephaner Steig 16, D-85350 Freising, Germany

Article history:

Received August 6, 2001
Accepted November 8, 2001

Key words:

thermophilic bacteria, canned food, anaerobic thermophiles, PCR, Thermoanaerobacter, Thermoanaerobacterium

Summary:

In order to determine the reason for loss of vacuum in canned food, obligately anaerobic, spore forming thermophilic organisms were isolated from shelf-stable canned food containing vegetables, noodles and potatoes as main ingredients. Thermophilic bacteria from 44 canned food samples that had been stored under anaerobic conditions at 37 °C for at least 7 days were isolated. In addition, organic fertilizer used for the cultivation of some of the foods’ ingredients was examined and anaerobic, thermophilic bacteria could also be isolated from this source. Identification of bacterial strains was carried out by partial and complete 16S-rRNA-gene sequencing. Some of the obtained gene sequences showed a high level of similarity to existing 16S-rRNA gene sequences towards strains of the genera Thermoanaerobacter, Thermoanaerobium and Thermoanaerobacterium respectively, which have not yet been reported to be of importance as food spoilers. In the course of identification of these thermophilic bacteria we developed genera specific PCR-based approaches for detecting isolates belonging to the genera Thermoanaeroacterium and Thermoanaerobacter. Direct capturing of free DNA from contaminated samples using oligonucleotides coupled with paramagentic beads allowed the reduction of the detection time to six hours with a lower limit of 104 cells/mL.



*Corresponding author:           m.ehrmann@lrz.tu-muenchen.de
                                               ++ 49 8161 71 3301
                                               ++ 49 8161 71 3327

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