RESUMO
AIMS: To test the effect of bovicin HC5 against vegetative cells and endospores of Alicyclobacillus acidoterrestris DSMZ 2498 in synthetic media and in acidic mango pulp. METHODS AND RESULTS: Alicyclobacillus acidoterrestris was grown in synthetic medium at 40 degrees C and pH 4.0. The effect on vegetative cells was assayed by adding bovicin HC5 to synthetic medium (40-160 AU ml(-1)) or to mango pulp (100 AU ml(-1)) at various pH values and determining the effect on growth (OD(600 nm)) and viable cell number, respectively. The effect of bovicin HC5 on spore germination and thermal sensitivity of A. acidoterrestris was tested in mango pulp (pH 4.0) containing 80 AU ml(-1) of bovicin HC5. Bovicin HC5 was bactericidal against vegetative cells of A. acidoterrestris at different pH values and showed sporicidal activity against endospores of this bacterium. When spores of A. acidoterrestris were heat treated in the presence of bovicin HC5, D-values decreased 77% to 95% compared to untreated controls at temperatures ranging from 80 to 95 degrees C. CONCLUSION: Bovicin HC5 was bactericidal and sporicidal against A. acidoterrestrsi DSMZ 2498. SIGNIFICANCE AND IMPACT OF THE STUDY: These results indicated that bovicin HC5 has potential to prevent spoilage of acidic fruit juices by thermocidophilic spore-forming bacteria.
Assuntos
Bacteriocinas/farmacologia , Bebidas , Microbiologia de Alimentos , Conservantes de Alimentos/farmacologia , Bacilos Gram-Positivos Formadores de Endosporo/efeitos dos fármacos , Mangifera , Extratos Vegetais , Técnicas Bacteriológicas , Germinação , Bacilos Gram-Positivos Formadores de Endosporo/fisiologia , Temperatura Alta , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/fisiologiaRESUMO
The adaptation time of Alicyclobacillus acidoterrestris CRA 7152 in orange juice was determined as a response to pH (3 to 5.8), temperature (20 to 54 degrees C), soluble solids concentration ((o)Brix; 11 to 19 (o)Brix), and nisin concentration (0 to 70 IU/ ml) effects. A four-factor central composite rotational design was used. Viable microorganisms were enumerated by plating on K medium (pH 3.7). Two primary models were used to represent growth and adaptation time. A second-order polynomial model was applied to analyze the effects of factors. Results showed that the Baranyi and Roberts model was better than the modified Gompertz model, considering the determination coefficient (R2) for experimental data description. Inhibition of bacteria can be obtained through several studied combinations for at least 47 days of storage. The shortest period of adaptation was observed between 37 to 45 degrees C, with pHs between 4 and 5, yet the longest periods of adaptation could be obtained around 20 degrees C with pHs close to 3.0. Statistical analysis of the quadratic model showed that the adaptation time increased as temperature or pH decreased, and as nisin concentration or soluble solids increased. The model showed that adaptation time has a minimum value for juice without nisin added, with 13.5% soluble solids, pH 5.0, and incubated at 43.8 degrees C. The statistical parameters that validated this model were an R2 of 0.816, a bias factor of 0.96, and an accuracy factor of 1.14. Manipulation of more than one factor, as well as the use of an antimicrobial agent, can be an alternative to preventing the development of A. acidoterrestris in orange juice, thus contributing to increased orange juice shelf life.
Assuntos
Adaptação Fisiológica , Antibacterianos/farmacologia , Bebidas/microbiologia , Conservação de Alimentos/métodos , Bacilos Gram-Positivos Formadores de Endosporo/fisiologia , Modelos Biológicos , Nisina/farmacologia , Citrus sinensis/microbiologia , Relação Dose-Resposta a Droga , Contaminação de Alimentos/análise , Manipulação de Alimentos/métodos , Microbiologia de Alimentos , Bacilos Gram-Positivos Formadores de Endosporo/efeitos dos fármacos , Bacilos Gram-Positivos Formadores de Endosporo/crescimento & desenvolvimento , Concentração de Íons de Hidrogênio , Cinética , Esporos Bacterianos/efeitos dos fármacos , Esporos Bacterianos/crescimento & desenvolvimento , Temperatura , Fatores de TempoRESUMO
Two sporulating bacterial strains designated CECAP06(T) and CECAP16 were isolated from the rhizosphere of the legume Cicer arietinum in Argentina. Almost-complete 16S rRNA gene sequences identified the isolates as a Paenibacillus species. It was most closely related to Paenibacillus cineris LMG 18439(T) (99.6 % sequence similarity), Paenibacillus favisporus LMG 20987(T) (99.4 % sequence similarity) and Paenibacillus azoreducens DSM 13822(T) (97.7 % sequence similarity). The cells of this novel species were motile, sporulating, rod-shaped, Gram-positive and strictly aerobic. The predominant fatty acids were anteiso-C(15 : 0), C(16 : 0) and iso-C(16 : 0). The DNA G+C content of strains CECAP06(T) and CECAP16 was 51.3 and 50.9 mol%, respectively. Growth was observed from many carbohydrates, but gas production was not observed from glucose. Catalase and oxidase activities were present. The isolates produced beta-galactosidase and hydrolysed aesculin. Gelatinase, caseinase and urease were not produced. The results of DNA-DNA hybridization showed that the strains from this study constitute a novel species of the genus Paenibacillus, for which the name Paenibacillus rhizosphaerae sp. nov. is proposed. The type strain is CECAP06(T) (=LMG 21955(T) = CECT 5831(T)).