Bovicin HC5 and nisin reduce cell viability and the thermal resistance of Alicyclobacillus acidoterrestris endospores in fruit juices.

BACKGROUND: Alicyclobacillus acidoterrestris is an important thermoacidophilic spore-forming bacterium in fruit-juice deterioration, and alternative non-thermal methods have been investigated to control fruit juice spoilage. This work aimed to evaluate the capacity of bovicin HC5 and nisin to inhibit the growth of vegetative cells and reduce the thermal resistance of endospores of A. acidoterrestris inoculated (107 CFU mL-1 ) in different fruit juices. The number of viable cells was determined after 12 h incubation at 43 °C in the presence and absence of nisin or bovicin HC5 (10-100 AU mL-1 ). The exposure time (min) required to kill 90% of the initial population (reduction of one log factor) at 90 ºC (D90ºC ) was used to assess the thermal resistance of A. acidoterrestris endospores exposed (80 AU mL-1 ) or non-exposed to the bacteriocins. Additionally, the effect of bovicin and nisin on the morphology and cell structure of A. acidoterrestris was evaluated by atomic force microscopy (AFM). RESULTS: Bovicin HC5 and nisin were bactericidal against A. acidoterrestris inoculated in fruit juices and reduced the D90°C values up to 30-fold. AFM topographical images revealed substantial structural changes in the cellular framework of vegetative cells upon treatment with bovicin HC5 or nisin. CONCLUSIONS: These results emphasize the potential application of lantibiotics as additional hurdles in food processing to control thermoacidophilic spoilage bacteria in fruit juices. © 2022 Society of Chemical Industry.

Effects of the oral administration of viable and heat-killed Streptococcus bovis HC5 cells to pre-sensitized BALB/c mice.

Antimicrobial peptides have been suggested as an alternative to classical antibiotics in livestock production and bacteriocin-producing bacteria could be added to animal feeds to deliver bacteriocins in the gastrointestinal (GI) tract of ruminant and monogastric animals. In this study, viable (V) and heat-killed (HK) Streptococcus bovis HC5 cells were orally administered to pre-sensitized mice in order to assess the effects of a bacteriocin-producing bacteria on histological parameters and the immune response of the GI tract of monogastric animals. The administration of V and HK S. bovis HC5 cells during 58 days to BALB/c mice did not affect weight gain, but an increase in gut permeability was detected in animals receiving the HK cells. Viable and heat killed cells caused similar morphological alterations in the GI tract of the animals, but the most prominent effects were detected in the small intestine. The oral administration of S. bovis HC5 also influenced cytokine production in the small intestine, and the immune-mediated activity differed between V and HK cells. The relative expression of IL-12 and INF-γ was significantly higher in the small intestine of mice treated with V cells, while an increase in IL-5, IL-13 and TNF-α expression was only detected in mice treated with HK cells. Considering that even under a condition of severe challenge (pre-sensitization followed by daily exposure to the same bacterial immunogen) the general health of the animals was maintained, it appears that oral administration of S. bovis HC5 cells could be a useful route to deliver bacteriocin in the GI tract of livestock animals.