Table of Contents
ISRN Microbiology
Volume 2013, Article ID 731430, 6 pages
http://dx.doi.org/10.1155/2013/731430
Research Article

Growth Limiting pH, Water Activity, and Temperature for Neurotoxigenic Strains of Clostridium butyricum

1Microbiology Research Unit, School of Human Sciences, London Metropolitan University, London N7 8DB, UK
2Department of Food & Nutritional Sciences, The University of Reading, Whiteknights, Reading RG6 6AP, UK
3Department of Microbiology, University of Lagos, Lagos 100223, Nigeria

Received 16 July 2013; Accepted 25 August 2013

Academic Editors: G. Blaiotta and D. Y. C. Fung

Copyright © 2013 Hamid B. Ghoddusi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Some rare strains of Clostridium butyricum carry the gene encoding the botulinal type E neurotoxin and must be considered as possible hazards in certain types of food. The limiting growth conditions for C. butyricum were determined in peptone yeast glucose starch (PYGS) broth incubated anaerobically at 30°C for up to 42 days. The minimum pH values permitting growth depended on the acidulant and strain. Organic acids were more effective at inhibiting growth than HCl as expected. The lowest pH values at which growth of toxigenic and nontoxigenic strains of C. butyricum was observed in broth acidified with HCl were 4.1 and 4.2, respectively. In organic acids, however, the minimum pH varied between 4.4 and 5.1 depending on acid type and concentration. The minimum water activity for growth of toxigenic strains of C. butyricum was 0.96. The minimum growth temperatures of the toxigenic strains of C. butyricum (ca 10-11°C) were somewhat higher than for non-toxigenic ones (8°C). It was concluded that control of toxigenic C. butyricum in the food industry needs to allow for the greater pH tolerance of this species compared with proteolytic C. botulinum.