title: Clostridium tyrobutyricum strains show wide variation in growth at different NaCl, pH, and temperature conditions.
abstract: Outgrowth from Clostridium tyrobutyricum spores in milk can lead to butyric acid fermentation in cheeses, causing spoilage and economical loss to the dairy industry. The aim of this study was to investigate the growth of 10 C. tyrobutyricum strains at different NaCl, pH,  and temperature conditions. Up to 7.5-fold differences among the maximum growth rates of different strains in the presence of 2.0% NaCl were observed. Five of 10 strains were able to grow in the presence of 3.0% NaCl, while a NaCl concentration of 3.5% was completely inhibitory to all strains.  Seven of 10 strains were able to grow at pH 5.0, and up to 4- and 12.5-fold differences were observed among the maximum growth rates of different strains at pH 5.5 and 7.5, respectively. The maximum growth temperatures varied from 40.2 to 43.3°C. The temperature of 10°C inhibited the  growth of all strains, while 8 of 10 strains grew at 12 and 15°C. Despite showing no growth, all strains were able to survive at 10°C. In conclusion, wide variation was observed among different C. tyrobutyricum strains in their ability to grow at different stressful conditions.  Understanding the physiological diversity among the strains is important when designing food control measures and predictive models for the growth of spoilage organisms in cheese.
authors.affiliation: Department of Food Hygiene and Environmental Health, Faculty of Veterinary Medicine, P.O. Box 66, 00014 University of Helsinki, Finland. marjo.ruusunen@helsinki.fi
authors.forename: Marjo
authors.initials: M
authors.lastname: Ruusunen
authors.forename: Anu
authors.initials: A
authors.lastname: Surakka
authors.forename: Hannu
authors.initials: H
authors.lastname: Korkeala
authors.forename: Miia
authors.initials: M
authors.lastname: Lindström
mesh_terms: D000818:Animals; D019540:Area Under Curve; D002611:Cheese / Q000382:microbiology; D048014:Clostridium tyrobutyricum / Q000187:drug effects / Q000254:growth & development*; D015169:Colony Count, Microbial / Q000379:methods; D004305:Dose-Response Relationship, Drug; D005506:Food Contamination / Q000032:analysis; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D059022:Food Safety; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008892:Milk / Q000382:microbiology; D008954:Models, Biological; D012965:Sodium Chloride / Q000494:pharmacology*; D013171:Spores, Bacterial; D013696:Temperature
chemical_list: D012965:Sodium Chloride