RESUMO
Alicyclobacillus spp. is the cause of great concern for the food industry due to their spores' resistance (thermal and chemical) and the spoilage potential of some species. Despite this, not all Alicyclobacillus strains can spoil fruit juices. Thus, this study aimed to identify Alicyclobacillus spp. strains isolated from fruit-based products produced in Argentina, Brazil, and Italy by DNA sequencing. All Alicyclobacillus isolates were tested for guaiacol production by the peroxidase method. Positive strains for guaiacol production were individually inoculated at concentration of 103 CFU/mL in 10 mL of orange (pH 3.90) and apple (pH 3.50) juices adjusted to 11°Brix, following incubation at 45 °C for at least 5 days to induce the production of the following spoilage compounds: Guaiacol, 2,6-dichlorophenol (2,6-DCP) and 2,6-dibromophenol (2,6-DBP). The techniques of micro-solid phase extraction by headspace (HS-SPME) and gas-chromatography with mass spectrometry (GC-MS) were used to identify and quantify the spoilage compounds. All GC-MS data was analyzed by principal component analysis (PCA). The effects of different thermal shock conditions on the recovery of Alicyclobacillus spores inoculated in orange and apple juice (11°Brix) were also tested. A total of 484 strains were isolated from 48 brands, and the species A. acidocaldarius and A. acidoterrestris were the most found among all samples analyzed. In some samples from Argentina, the species A. vulcanalis and A. mali were also identified. The incidence of these two main species of Alicyclobacillus in this study was mainly in products from pear (n = 108; 22.3 %), peach (n = 99; 20.5 %), apple (n = 86; 17.8 %), and tomato (n = 63; 13 %). The results indicated that from the total isolates from Argentina (n = 414), Brazil (n = 54) and Italy (n = 16) were able to produce guaiacol: 107 (25.8 %), 33 (61.1 %) and 13 (81.2 %) isolates from each country, respectively. The PCA score plot indicated that the Argentina and Brazil isolates correlate with higher production of guaiacol and 2,6-DCP/2,6-DBP, respectively. Heatmaps of cell survival after heat shock demonstrated that strains with different levels of guaiacol production present different resistances according to spoilage ability. None of the Alicyclobacillus isolates survived heat shocks at 120 °C for 3 min. This work provides insights into the incidence, spoilage potential, and thermal shock resistance of Alicyclobacillus strains isolated from fruit-based products.
Assuntos
Alicyclobacillus , Sucos de Frutas e Vegetais , Frutas , Cromatografia Gasosa-Espectrometria de Massas , Guaiacol , Esporos Bacterianos , Alicyclobacillus/isolamento & purificação , Alicyclobacillus/genética , Alicyclobacillus/classificação , Alicyclobacillus/crescimento & desenvolvimento , Sucos de Frutas e Vegetais/microbiologia , Guaiacol/análogos & derivados , Guaiacol/metabolismo , Guaiacol/farmacologia , Frutas/microbiologia , Esporos Bacterianos/crescimento & desenvolvimento , Esporos Bacterianos/isolamento & purificação , Microbiologia de Alimentos , Contaminação de Alimentos/análise , Brasil , Microextração em Fase Sólida , Argentina , Malus/microbiologia , Itália , Temperatura Alta , Citrus sinensis/microbiologiaRESUMO
Bacteria of the genus Alicyclobacillus pose serious quality problems for the juice processing industries that have sought effective alternatives for its control. The present study evaluated the effect of UV-C radiation on the reduction of spores and biofilm formation of Alicyclobacillus spp. on stainless steel and rubber surfaces using industrialized orange juice as a culture medium. Four reference Alicyclobacillus spp. species and different UV-C dosages were investigated. After exposed for 20â¯min (16.8â¯kJ/m2) to UV-C, the spores of Alicyclobacillus acidoterrestris, Alicyclobacillus herbarius, and Alicyclobacillus cycloheptanicus decreased drastically more of 4 log CFU/mL, with counts below the detection limit of the method (<1.7 log CFU/mL), while the Alicyclobacillus acidocaldarius spores were more sensitive to UV-C, once this spore reduction was observed within 15â¯min (12.6â¯kJ/m2). Morphological changes in the Alicyclobacillus acidoterrestris spores were observed by scanning electron microscopy. A reduction of biofilm formation was observed for all UV-C treatments, and the higher reductions (approximately 2 log CFU/mL) were found for the Alicyclobacillus acidocaldarius species after 30â¯min (26.2â¯kJ/m2), on the stainless steel and rubber surfaces. The results suggest that UV-C can be used to reduce the biofilm formation and could be a promising alternative for controlling Alicyclobacillus spp. spores in industrialized orange juice.
Assuntos
Alicyclobacillus/efeitos da radiação , Biofilmes/efeitos da radiação , Citrus sinensis/química , Irradiação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Esporos Bacterianos/efeitos da radiação , Alicyclobacillus/classificação , Alicyclobacillus/crescimento & desenvolvimento , Alicyclobacillus/isolamento & purificação , Manipulação de Alimentos/instrumentação , Microbiologia de Alimentos , Esporos Bacterianos/crescimento & desenvolvimento , Aço Inoxidável/análise , Raios UltravioletaRESUMO
Three morphologically similar thermo-acidophilic strains, USBA-GBX-501, USBA-GBX-502 and USBA-GBX-503T, were isolated from acidic thermal springs at the National Natural Park Los Nevados (Colombia). All isolates were spore-forming, Gram-stain-positive and motile, growing aerobically at 25-55 °C (optimum ~45 °C) and at pH 1.5-4.5 (optimum pH ~3.0). Phylogenetic analysis of the 16S rRNA gene sequences of these isolates showed an almost identical sequence (99.0â% similarity) and they formed a robust cluster with the closest relative Alicyclobacillus tolerans DSM 16297T with a sequence similarity of 99.0â%. Average similarity to other species of the genus Alicyclobacillus was 93.0â% and average similarity to species of the genus Effusibacillus was 90â%. In addition, the level of DNA-DNA hybridization between strain USBA-GBX-503T and Alicyclobacillus tolerans DSM 16297T was 31.7â%. The genomic DNA G+C content of strain USBA-GBX-503T was 44.6 mol%. The only menaquinone was MK-7 (100.0â%). No ω-alicyclic fatty acids were detected in strain USBA-GBX-503T, and the major cellular fatty acids were C18â:â1ω7c, anteiso-C17â:â0 and iso-C17â:â0. Based on phenotypic and chemotaxonomic characteristics, phylogenetic analysis and DNA-DNA relatedness values, along with low levels of identity at the whole genome level (ANIb and ANIm values of <67.0 and <91.0â%, respectively), it can be concluded that strain USBA-GBX-503T represents a novel species of the genus Alicyclobacillus, for which the name Alicyclobacillus montanus sp. nov. is proposed. The type strain is USBA-GBX-503T (=CMPUJ UGB U503T=CBMAI1927T).
Assuntos
Alicyclobacillus/classificação , Fontes Termais/microbiologia , Filogenia , Alicyclobacillus/genética , Alicyclobacillus/isolamento & purificação , Técnicas de Tipagem Bacteriana , Composição de Bases , Colômbia , DNA Bacteriano/genética , Ácidos Graxos/química , Hibridização de Ácido Nucleico , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Vitamina K 2/análogos & derivados , Vitamina K 2/químicaRESUMO
In this study, the population of Alicyclobacillus spp. was estimated in pasteurized exotic Brazilian fruit juices using the most probable number (MPN) technique followed by biochemical tests. Pasteurized passion fruit (n = 57) and pineapple (n = 50) juices were taken directly from Brazilian manufacturers. While Alicyclobacillus spp. was isolated from passion fruit juice, the microorganism was not found in any pineapple juice samples. A higher incidence of Alicyclobacillus was observed in samples taken in June and July (dry months in Brazil) in comparison to the other months (March, April, May and August), and the highest Alicyclobacillus counts were recovered from these samples(>23 MNP/100 mL). Sixteen (n = 16) Alicyclobacillus strains were typed using the randomly amplified polymorphic DNA method (RAPD-PCR). RAPD-PCR revealed great genetic similarity between the passion fruit juice strains and Alicyclobacillus acidoterrestris DSM 2498. The heat resistance of three isolates was determined, and the mean D(95°) (1.7 min) and z (7.6 °C) values in the passion fruit juice were not significantly different (p > 0.05) from those obtained for the DSM 2498 strain (D(95°) = 1.5 min and z = 7.1 °C). This is the first report on the isolation of A. acidoterrestris from exotic fruit juices such as passion fruit juice. It is worth pointing out the importance of applying good agricultural practices in the field and applying controls for the fruit selection and washing steps, as well as controlling the time/temperature conditions for pasteurization so as to reduce the incidence and chances of A. acidoterrestris spoilage in these juices.