Resistance to preservatives and the viable but non-culturable state formation of Asaia lannensis in flavored syrups

Xia Wen; Yiwen Chen; Shuyao Zhang; Ai-Ting Su; Di Huang; Gang Zhou; Xiaobao Xie; Jufang Wang

doi:10.3389/fmicb.2024.1345800

Resistance to preservatives and the viable but non-culturable state formation of Asaia lannensis in flavored syrups

Front Microbiol. 2024 Feb 16:15:1345800. doi: 10.3389/fmicb.2024.1345800. eCollection 2024.

Authors

Xia Wen^{1

2

3}, Yiwen Chen³, Shuyao Zhang³, Ai-Ting Su³, Di Huang³, Gang Zhou³, Xiaobao Xie³, Jufang Wang^{1

2}

Affiliations

¹ School of Biology and Biological Engineering, South China University of Technology, Guangzhou, China.
² Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou, China.
³ Key Laboratory of Agricultural Microbiomics and Precision Application (Ministry of Agriculture and Rural Affairs), Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Key Laboratory of Agricultural Microbiome (Ministry of Agriculture and Rural Affairs), State Key Laboratory of Applied Microbiology Southern China, Guangdong Detection Center of Microbiology, Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.

Abstract

Food security is a crucial issue that has caused extensive concern, and the use of food flavors has become prevalent over time. we used the molecular biological techniques, preservative susceptibility testing, viable but non-culturable (VBNC) state induction testing, and a transcriptome analysis to examine the bacterial contamination of favored syrup and identify the causes and develop effective control measures. The results showed that Asaia lannensis WLS1-1 is a microorganism that can spoil food and is a member of the acetic acid bacteria families. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) tests showed that WLS1-1 was susceptible to potassium sorbate (PS), sodium benzoate (SB), and sodium sulffte (SS) at pH 4.0. It revealed a progressive increase in resistance to these preservatives at increasing pH values. WLS1-1 was resistant to PS, SB and SS with an MIC of 4.0, 2.0 and 0.5 g/L at pH 5.0, respectively. The MIC values exceed the maximum permissible concentrations that can be added. The induction test of the VBNC state demonstrated that WLS1-1 lost its ability to grow after 321 days of PS induction, 229 days of SB induction and 52 days of SS induction combined with low temperature at 4°C. Additionally, laser confocal microscopy and a propidium monoazide-quantitative polymerase chain reaction (PMA-qPCR) assay showed that WLS1-1 was still alive after VBNC formation. There were 7.192 ± 0.081 (PS), 5.416 ± 0.149 (SB) and 2.837 ± 0.134 (SS) log₁₀(CFU/mL) of viable bacteria. An analysis of the transcriptome data suggests that Asaia lannensis can enter the VBNC state by regulating oxidative stress and decreasing protein synthesis and metabolic activity in response to low temperature and preservatives. The relative resistance of Asaia lannensis to preservatives and the induction of the VBNC state by preservatives are the primary factors that contribute to the contamination of favored syrup by this bacterium. To our knowledge, this study represents the first evidence of the ability of Asaia lannensis to enter the VBNC state and provides a theoretical foundation for the control of organisms with similar types of activity.

Keywords: Asaia lannensis; VBNC; flavored syrups; preservatives; resistance.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the Research and Development Plan for Key Fields of Guangdong Province (no. 2022B1111040002), the GDAS Special Project of Science and Technology Development (nos. 2022GDASZH-2022010101; 2020GDASYL-20200103030), and the Natural Science Foundation of Guangdong Province (no. 2023A1515012057).