Modelling of the acid–base properties of two thermophilic bacteria at different growth times

Quantitative assessment of the risk of microbial spoilage in foods. Prediction of non-stability at 55°C caused by Geobacillus stearothermophilus in canned green beans

“…Specific laboratory experiments to determine the growth rate of spores of G. stearothermophilus strains (CTCPA 2804 173, 2804 138, 2804 168) were produced as previously described (André et al, 2012) and separately spiked at 10 spores/g and 10 2 spores/g in 50 g of green beans in 50 ml of brine. Despite suboptimal pH, μ max was of the same order of magnitude as that observed in other media and foods (Heinrich et al, 2008;Ng and Schaffner, 1997;Ng et al, 2002;Thompson and Thames, 1967;Yoo et al, 2006). We therefore assumed that canned green beans were a highly suitable medium for G. stearothermophilus growth and set the most likely value of μ opt at 2.3 h − 1 , based on the cell doubling time T d reported by Llaudes et al (2001) in tryptic soy broth (μ opt = ln(2) / T d ).…”

“…The pH of the sterilized product in which growth will occur was estimated at 5.5 pH unit on average, based on specific measurements (Section 2.3). G. stearothermophilus C max values are between 10 7 and 10 11 (Thompson and Thames, 1967;Ng and Schaffner, 1997;Yoo et al, 2006;Heinrich et al, 2008;André unpublished data 2011). Mean C max was taken at 10 9 , which is the middle of the range (on a log 10 scale) of these previously reported values.…”

Proton and cadmium adsorption by the archaeon Thermococcus zilligii: Generalising the contrast between thermophiles and mesophiles as sorbents

“…Most previous investigations of proton and metal adsorption by bacteria have involved mesophilic species (optimal growth temperatures in the range 20-40°C), but several recent investigations have focussed on proton and/or metal adsorption by thermophilic bacteria Hetzer et al, 2006;Burnett et al, 2006aBurnett et al, ,b, 2007Heinrich et al, 2007Heinrich et al, , 2008Ginn and Fein, 2008;Lalonde et al, 2008;Tourney et al, 2008;Özdemir et al, 2009). Surface Complexation Models (SCMs) have been developed to describe proton and metal adsorption by both thermophilic and mesophilic bacteria, and can provide a framework for assessing any differences that might exist in the adsorptive properties of the two groups, through comparison of model parameters.…”

“…Various electric double layer models have been integrated into SCMs to determine the electric potential of the cell surface, including the constant capacitance model (Fein et al, 1997;Daughney et al, 1998;Ngwenya et al, 2003), the Stern model (Daughney and Fein, 1998), the diffuse layer and triple layer models ) and the Donnan model (Yee et al, 2004, Burnett et al, 2006aHeinrich et al, 2007Heinrich et al, , 2008.…”

“…In this study, we follow the approach of and use a consistent modelling framework to re-develop SCMs for proton and Cd adsorption by the archaeon T. zilligii and previously studied thermophilic bacteria Hetzer et al, 2006;Burnett et al, 2006aBurnett et al, ,b, 2007Heinrich et al, 2007Heinrich et al, , 2008Ginn and Fein, 2008;Tourney et al, 2008). The same SCM framework is employed to re-develop universal SCMs for proton and Cd adsorption by mesophilic bacteria (Yee and Fein, 2001;Johnson et al, 2007).…”