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| Development and application of Saccharomyces cerevisiae reference material for the metrological evaluation of biological sampling efficiency of planktonic bacteria sampler |
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Abstract Biological sampling efficiency is an important performance indicator of planktonic bacteria sampler, in response to the lack of fungal model microorganism reference material and evaluation method, central composite design method was used to optimise the formulation of the protective agents of reference material, the effects of two different pre-freezing methods (liquid nitrogen quick-freezing method and -80℃ slow-freezing method) on the survival rate of Saccharomyces cerevisiae were compared. The homogeneity, stability and value of the reference material were also evaluated. The test conditions of the biological sampling efficiency evaluation were researched. The concentration of Saccharomyces cerevisiae suspension for aerosol generation, humidity and sampling time were optimized by comparing different reference samplers. With the selected Andersen six-stage as the reference sampler, the biological sampling efficiency of planktonic bacteria sampler BAS C230 was evaluated. The results showed that the optimal concentration (W/V) of the freeze-dried protectants for Saccharomyces cerevisiae were: skimmed milk powder 8.05%, trehalose 9%, protectant a 1.41%, protectant b 1.5%, and protectant c 0.011%, where protectant a could increase the survival rate of Saccharomyces cerevisiae by about 9.0%. -80°C slow freezing for 2 h followed by freeze-drying, the survival rate of yeast was higher than that of liquid nitrogen quick-freezing. Finally, freeze-dried Saccharomyces cerevisiae reference material of the value of 8.65×106CFU/bottle with relative expanded uncertainty of 4.32%（k=2）was obtained, with a survival rate of 81.2%±1.4% and good homogeneity and stability. It has good solubility and the concentration of its suspension liquid is easy to adjust. The Saccharomyces cerevisiae in bioaerosol can be captured by the reference sampler and the tested sampler and grow well on the medium plate, which indicated that the Saccharomyces cerevisiae reference material and the method can be applied in the metrological evaluation of the biological sampling efficiency of planktonic bacteria sampler successfully.
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Received: 30 May 2024
Published: 19 March 2025
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2025, Vol. 46 
