Effect of Environmental Conditions on the Formation of the Viable but Nonculturable State of Pediococcus acidilactici BM-PA17927 and Its Control and Detection in Food System

Abstract

This study aimed to investigate the effect of environmental conditions including nutrient content, acetic acid concentration, salt concentration, and temperature on the formation of viable but nonculturable (VBNC) state of Pediococcus acidilactici, as well as its control and detection in food system. Methods: Representing various environmental conditions in different food systems, 16 induction groups were designed for the formation of VBNC state of P. acidilactici. Traditional plate counting was applied to measure the culturable cell numbers, and Live/Dead Bacterial Viability Kit combined with fluorescent microscopy was used to identify viable cells numbers. The inhibition of bacterial growth and VBNC state formation by adjusting the environmental conditions were investigated, and the clearance effect of VBNC cells in crystal cake system was studied. In addition, a propidium monoazide-polymerase chain reaction (PMA-PCR) assay was applied to detect the VBNC P. acidilactici cells in crystal cake food system. Results: Among the environmental conditions included in this study, acetic acid concentration had the greatest effect on the formation of VBNC state of P. acidilactici, followed by nutritional conditions and salt concentration. Reducing nutrients in the environment and treating with 1.0% acetic acid can inhibit P. acidilactici from entering the VBNC state. In the crystal cake system, the growth of P. acidilactici and the formation of VBNC state can be inhibited by adding 1.0% acetic acid and storing at −20°C. In crystal cake system, the PMA-PCR assay can be used to detect VBNC P. acidilactici cells at a concentration higher than 10 4 cells/ml. Li et al.

Pseudomonas aeruginosa: A typical biofilm forming pathogen and an emerging but underestimated pathogen in food processing

“…Complex microbial communities also exist in a range of vegetables and fruits besides the foods described above ( Li et al, 2020a , b , c , d ), and endophytic and exterior parasitic P. aeruginosa has been normally isolated in fresh, raw vegetables and fruits, for example, cucumber, minitomatoes, tomatoes, onion, carrots, lettuces, spinaches, celeries, and different types of salads ( Remington and Schimpff, 1981 ; Xu et al, 2019 ). Pseudomonas spp.…”

Biofilm formation of two genetically diverse Staphylococcus aureus isolates under beta-lactam antibiotics

“…Biofilm and VBNC formation are both significant concerns in food safety, and their formation is also closely relevant to the incubation conditions. Previously, condition mimicking food processing have been used to inhibit biofilm or VBNC formation ( Liu et al, 2018a , 2019 ; Li et al, 2020a , b , c ; Wei et al, 2020 ). Initially, antibiotics have also been considered to be an agent employed for biofilm or VBNC formation, and generally speaking, antibiotics have an inhibitory effect on the growth of microorganisms and thus should inhibit the formation of biofilms.…”

Formic acid, an organic acid food preservative, induces viable-but-non-culturable state, and triggers new Antimicrobial Resistance traits in Acinetobacter baumannii and Klebsiella pneumoniae

“…Subsequently, reports on food processing techniques, including pasteurizing milk, brewing beer, and chlorinating water, that facilitate the conversion of bacteria to the VBNC form further increased a vast interest in this topic ( Oliver and Bockian, 1995 ; Liu et al, 2018b ; Xu et al, 2020 ). The use of acetic acid as a food preservative along with incubation in a freezing temperature induced VBNC forms in Pediococcus acidilactici ( Li et al, 2020a ).…”