Kinetics of Death of Bacterial Spores at Elevated Temperatures

Abstract

The kinetics of death of Bacillus stearothermophilus spores (FS 7954) suspended in phosphate buffer (pH 7) were studied over a temperature range of 127.2 to 143.8 C and exposure times of 0.203 to 4.150 sec. These short exposure were achieved by use of a tubular flow reactor in which a suspension of spores was injected into a hot flowing stream at the entrance of the reactor. Thermal equilibria of the suspension with the hot stream was achieved within 0.0006 sec. After flow through a fixed length of reactor, the stream containing the spores was cooled by flash vaporization and then assayed for viable count. The death rate data were fitted by a logarithmic expression. However, logarithmic death rate was only approximated in the tail or high-kill regions of exposure. Death rate constants obtained from this portion of the data were found to correlate by Arrhenius as well as Absolute Reaction Rate Theory relationships. Thermal-death time curves were found to correlate the data rather poorly. The activation energy and frequency constant for an Arrhenius relationship fit of the data were found to be 83.6 kcal/gmole and 10 47.2 min -1 , respectively. The standard enthalpy and entropy changes for an Absolute Reaction Rate Theory relationship fit of the data were found to be 84.4 kcal/gmole and 157 cal/gmole-K, respectively.

Simulation of thermal sanitization of air with heat recovery as applied to airborne pathogen deactivation

“…Values of the pre-exponential and activation energy of the constant k of the first-order reaction of thermal inactivation. k in min −1 Microorganism ln( A ) Ea (kJ mol −1 ) Refs Lipopolysaccharides 24 96.7 Tsuji and Harrison ( 1978 ) Clostridium tetani (NCTC 5411 and 5413) 23.9 151.8 Darmady et al ( 1961 ) Hepatitis A virus 58.1 163.7 Bozkurt et al ( 2014 ) RNA viruses (Hemorrhagic fever) 34.1 36.7 Madani et al ( 2014 ) SARS-CoV-2 48.6 135.7 Yap et al ( 2020 ) SARS-CoV-1 51.9 141.6 Yap et al ( 2020 ) Gastroenteritis Virus-RH50 36.8 106 Yap et al ( 2020 ) Clostridium Botulinum bacteria 105.2 307.9 Davey ( 1993 ) Bacillus stearothermophilus spores 108.7 349.8 Wang et al ( 1964 ) Bacillus stearothermophilus spores 104.5 339.8 Abraham et al ( ...…”

Desenvolvimento, construção e validação de reator para determinação do efeito da tensão de cisalhamento na resistencia termica de microrganismos

“…O mais antigo, e mais usado até hoje, é o método do tubo TDT selado. Busta (1967) reportou diferenças significativas para as constantes térmicas de inativação (valores D e z) encontradas por ele e por outros pesquisadores (Esselen e Pflug, 1956;Franklin et al, 1959;Stumbo et al, 1950;Wang et al, 1964), para B. stearothermophilus inoculado em sistema UHT, quando comparado ao sistema TDT. Burton et al(1977) também indicaram diferenças entre os valores dos parâmetros cinéticos de destruição térmica determinados pelo método do tubo TDT e em sistemas contínuos; estes autores verificaram que os resultados para morte térmica de Bacillus stearothermophilus em um processo contínuo e em tubo TDT a temperaturas inferiores a 145ºC não coincidiam, sendo que a taxa de morte térmica a 137ºC, em processo contínuo, era metade daquela verificada no tubo 13 TDT.…”