Foodborne bacteria produce biofilms and their viable but non-culturable (VBNC) formation, can affect food quality and safety. Studies have shown that these characteristics are regulated by the bacterial quorum sensing (QS) system. Quenching the QS system of foodborne bacteria and blocking the expression of the corresponding genes may be an effective way to improve food quality and safety. Therefore, this article reviews the QS systems for foodborne bacteria, the regulatory mechanisms of QS systems in biofilm and VBNC formation and resuscitation, the research progress on quorum sensing inhibitors (QSIs) for Gram-negative and Gram-positive bacteria, and introduces QSIs from various sources. In addition, we have also summarized the current research issues on QS regulation of biofilms and VBNC formation. The systematic study of the QS phenomenon of foodborne bacteria in practical situations, the mechanism of bacterial QS cooperation-cheating, the screening of novel and highly active QSIs, the combination of QSIs and other technologies to improve their bioavailability, and the regulatory network between biofilm and VBNC formation and resuscitation are research directions that need to be paid attention to in the future.

In this study, we utilized gene knockout and overexpression techniques to generate brewer’s yeast strains with either a deletion or overexpression of the fatty acyl-CoA oxidase (POX1) gene. The strains studied included the parental strain, the POX1 deletion strain, and the POX1 overexpression strain. These strains were exposed to iso-α acid from hops at a concentration of 300 mg/L, leading to the induction of a viable but non-culturable (VBNC) state. Our results indicated that the silencing of the POX1 gene rendered brewer’s yeast cells unable to withstand the high concentration of iso-α acid stress, ultimately leading to cell death. Conversely, the overexpression of POX1 accelerated the transition of yeast cells into the VBNC state compared to the parental strain. Furthermore, we evaluated the levels of reactive oxygen species (ROS), catalase (CAT) activity, superoxide dismutase (SOD) activity, glutathione reductase (GR) activity, and the mRNA expression of genes that regulate these enzymes (the stress-inducible yeast Mpv17 (SYM1) gene, CTA1, SOD1, and glutathione reductase (GLR1) gene) in brewer’s yeast cells at three distinct stages: normal, short-term stress, and VBNC states. Based on these findings, it can be inferred that the formation of the VBNC state in brewer’s yeast is associated with the response to oxidative stress.

Alpha-lactalbumin (α-LA) is a major whey protein found in breast milk and plays a crucial role in the growth and development of infants. In this study, Bacillus subtilis RIK1285 harboring AprE signal peptide (SP) was selected as the original strain for the production of α-LA. It was found that α-LA was identified in the pellet after ultrasonic disruption and centrifugation instead of in the fermentation supernatant. The original strain most likely only produced α-LA intracellular, but not extracellular. To improve the expression and secretion of α-LA in RIK1285, a library of 173 homologous SPs from the B. subtilis 168 genome was fused with target LALBA gene in the pBE-S vector and expressed extracellularly in RIK1285. SP YjcN was determined to be the best signal peptide. Bands in supernatant were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and purified by nickel column to calculate the highest yield signal peptide. In addition, different promoters (P_aprE, P₄₃, and P_glv) were compared and applied. The results indicated that the strain RIK1285-pBE-P_glv-YjcN-LALBA had the highest α-LA yield, reaching 122.04 μg/mL. This study demonstrates successful expression and secretion of human α-LA in B. subtilis and establishes a foundation for simulating breast milk for infant formulas and developing bioengineered milk.