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Engineering Considerations for Cleaning and Disinfection in the Food Industry
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Kylee R. Goode, David Phinney, Tony Hasting, Peter Fryer
In this chapter, cleaning and disinfection (also commonly called sanitization) are discussed:Cleaning primarily refers to the removal of material from a surface.Disinfection or sanitization refers to the inactivation of pathogens and microbes, which occurs at different rates for different microbes depending on the inactivation approach.Sterilization refers to the destruction of all viable microorganisms, typically a 12 log reduction (99.9999999999%) in vegetative cells and a 7 log reduction in spores. A microbial “kill step” such as pasteurization or sterilization is normally applied to the product during production, not as part of cleaning.
Regulatory Compliance
Published in Sarfaraz K. Niazi, Disposable Bioprocessing Systems, 2016
SALs can be used to describe the microbial population that was destroyed by the sterilization process. Each log reduction (10−1) represents a 90% reduction in microbial population. So, a process shown to achieve a “6-log reduction” (10−6) will reduce a population from a million organisms (106) to very close to zero, theoretically. It is common to employ overkill cycles to provide the greatest assurance of sterility for critical products such as implantable devices.
Detection of respiration changes inside biofilms with microelectrodes during exposure to antibiotics
Published in Journal of Environmental Science and Health, Part A, 2019
Jun Lin, Zechen Wang, Yue Zang, Dong Zhang, Qing Xin
Biofilms are structured aggregations of microbial communities that adhere to solid surfaces. Compared to planktonic cells, which are exposed to relatively uniform environmental conditions, cells within a biofilm are encased in a self-produced matrix.[7] The formation of biofilms gives the subpopulation the ability to withstand antibiotic concentrations that would normally kill free-swimming planktonic cells, and therefore allow biofilm-based infections to persist chronically in spite of antibiotic therapy.[8] Because of the complex structure of biofilms, studying the influence of antibiotics is difficult. Traditional susceptibility testing for biofilms is not particularly different than that for planktonic cells, with the exceptional of additional pretreatments for biomass harvesting. In a common procedure, obtained cells are harvested, followed by resuspension, dilution and plating. After incubation, visible colonies can be counted to calculate the log reduction after antibiotics exposure. This method is quantitative and straightforward for planktonic cells, but is not as successful for biofilms. Because of the heterogeneity of biofilms, assessing them as a whole instead of distinct subpopulations may bring in evitable inaccuracies or the loss of some detailed information.[9] Moreover, biomass harvesting via removing biomass from the substratum by means of scraping, extrusion or sonication involves biofilm destruction, which makes in situ testing impossible.
Asymmetrical zinc(II) phthalocyanines conjugated to metal tungstate nanoparticles for photoinactivation of Staphylococcus aureus
Published in Journal of Coordination Chemistry, 2022
Sithi Mgidlana, Muthumuni Managa, Tebello Nyokong
The PACT studies were performed in 2% DMSO/PBS. Dark toxicity studies were done to verify that the micro-organism inactivation was due solely from the introduction of light. The Pc complexes and nanoconjugates showed no significant dark toxicity even at high concentrations (Figure S6). Concentration optimization of the nanoparticles and the nanoconjugates was done to obtain the minimum concentration that completely obliterates the bacteria within 60 min under light exposure. During the bacteria concentration optimization, dilution factor of 10−5 (1 × 109 CFU/mL) was observed to be the best for this study. The antibacterial activity of the solvent mixture (2% DMSO, control) was tested, and it was discovered that it had no effect on the cells. Figure 7 shows the PACT activity of selected Pc and conjugates. Log reduction provides a quantitative measurement that describes the percentage of microorganism that has been killed. Log reduction is calculated using Equation (2):where A is the number of viable bacteria pre-treatment and B is the number of viable bacteria post-treatment. Under illumination, nanoparticles (Bi2WO6, NiWO4, CoWO4) alone showed similar antimicrobial action (Figure S7). Considering complexes 4–6, containing acetophenone groups, there are considerable similarities in antimicrobial activity of 4 and 5 while 6 showed a larger PACT activity (Table 1). The antibacterial properties of Pc complexes 4–6 could be due to the presence of acetophenone substituents as reported [36]. Acetophenone derivatives show antibacterial activity [36]. For 6, the high log value can be attributed to acetic acid substituent, which has known antimicrobial properties [37] in addition to the high singlet oxygen generating ability. In addition, the reduced PACT activity of 1–3 might be due to the presence of 9 methoxy groups on the peripheral positions of the Pc. Methoxy groups are known to reduce antimicrobial activity, hence will reduce PACT activity of the Pcs [38].