ABSTRACT
El llamado queso artesanal de Corrientes (QAC) es un queso blando elaborado en la provincia de Corrientes a partir de leche de vaca cruda y agente coagulante artesanal. Las bacterias lácticas constituyen la flora principal de estos quesos, pero las levaduras también se encuentran en tasas elevadas como biota secundaria y podrían esempeñar un papel relevante en su maduración. El objetivo de este trabajo fue evaluar la presencia de levaduras en las materias primas y en la cuajada con la que se elabora este queso y durante su maduración en función de las variaciones estacionales. Se aislaron y purificaron levaduras a partir de la leche cruda, del agente coagulante, de la cuajada y de los quesos elaborados en las distintas estaciones del año a distintos tiempos de maduración. Los recuentos de levaduras fueron del orden de 10³ a 10(7) UFC/ml o UFC/g. Se obtuvieron e identificaron 90 cepas de levaduras: 9 de leche, 28 de agente coagulante, 10 de cuajada y 43 de quesos. En leche se observó un muy amplio predominio del género Candida, la incidencia de otros géneros fue poco significativa. En el agente coagulante también predominó netamente el género Candida, seguido por los géneros Myxozyma y Debaryomyces. Los aislamientos obtenidos de los quesos correspondieron a los mismos géneros que fueron predominantes en el agente coagulante, con el mismo orden de prevalencia.
The artisanal cheese from Corrientes (from the Spanish acronym QAC-Queso Artesanal de Corrientes/Artisanal Cheese from Corrientes) is a soft cheese elaborated with raw cow milk and an artisanal coagulant agent. Lactic bacteria contitute the main flora of this cheese although yeasts are also present in high quantities as secondary microbiota and might play a relevant role in cheese ripening. The aim of this work was to evaluate yeast occurrence during QAC elaboration and ripening, and the effect of seasonal variation. Yeasts were isolated and purified from raw materials and cheese at different ripening stagesl elaborated during the different seasons. Yeast sample counts were in the order of 10³ - 10(7) UFC/ml o UFC/g. Ninety yeast strains were classified: 9 from milk, 28 from the coagulant agent, 10 from curd and 43 from cheese. Candida predominated in milk samples while other yeast genera had low incidence. Candida also predominated in the coagulant agent samples, followed by genera Myxozyma and Debaryomyces. The isolates obtained from cheese belonged to the same genera predominating in the coagulant agent, and showed the same order of prevalence.
Subject(s)
Animals , Cattle , Female , Yeasts , Cheese , Microbiota , Argentina , Yeasts/isolation & purification , Cheese/microbiology , MilkABSTRACT
The artisanal cheese from Corrientes (from the Spanish acronym QAC-Queso Artesanal de Corrientes/Artisanal Cheese from Corrientes) is a soft cheese elaborated with raw cow milk and an artisanal coagulant agent. Lactic bacteria contitute the main flora of this cheese although yeasts are also present in high quantities as secondary microbiota and might play a relevant role in cheese ripening. The aim of this work was to evaluate yeast occurrence during QAC elaboration and ripening, and the effect of seasonal variation. Yeasts were isolated and purified from raw materials and cheese at different ripening stagesl elaborated during the different seasons. Yeast sample counts were in the order of 103 - 107UFC/ml o UFC/g. Ninety yeast strains were classified: 9 from milk, 28 from the coagulant agent, 10 from curd and 43 from cheese. Candida predominated in milk samples while other yeast genera had low incidence. Candida also predominated in the coagulant agent samples, followed by genera Myxozyma and Debaryomyces. The isolates obtained from cheese belonged to the same genera predominating in the coagulant agent, and showed the same order of prevalence.
Subject(s)
Cheese , Microbiota , Yeasts , Animals , Argentina , Cattle , Cheese/microbiology , Female , Milk , Yeasts/isolation & purificationABSTRACT
Plantaricin-149 is a bacteriocin produced by Lactobacillus plantarum NRIC 149 (a LAB isolated from pineapple), which consists of a peptidic chain made up of 22 amino acid residues [Kato et al. J. Ferment. Bioeng. 1994; 77: 277-282]. In this work, a synthetic C-terminal amidated peptide analog denoted Pln149a was prepared by SPPS-Fmoc chemistry and the antagonistic activity against gram-positive and gram-negative bacteria was tested. The secondary structure was studied by circular dichroism (CD) and the vicinity of the tyrosine residue by fluorescence spectroscopy under different conditions. We report the results of the interaction of Pln149a with reverse micelles prepared from the amphiphilic AOT in cyclohexane. Synthetic plantaricin was active against one strain of Staphylococcus aureus and four strains of Listeria genus at pH 5.5 and 7.4 and, like its natural variant, inhibited L. plantarum ATCC 8014. The data derived from spectroscopic measurements in presence of AOT reverse micelles suggest that the secondary structure of the peptide upon interaction is an alpha-helix. In this membrane model, the hydrophobic side of the alpha-helix is inserted into the micelles, leaving the lysines exposed to the solvent and interacting with the polar moieties of AOT. The fluorescence data point out that the N-terminal tyrosine residue is close to the micellar interface.
