Uso de métodos moleculares para la identificación de especies de levaduras aisladas de fermentaciones de aceitunas de mesa producidas tradicionalmente en Kahramanmaraş

In this study, yeast species involved in the naturally fermented green table olive produced in Southern Turkey were investigated. Table olive samples were prepared with regional olive cultivars and traditional methods were employed in the production. Yeasts were isolated from the brines of the samples at the late fermentation stage and identified at the species level by the DNA sequences of the D1/D2 domain of 26S rRNA genes. The D1/D2 domains were amplified by PCR, sequenced and compared to reference sequences deposited in the NCBI database. According to the results, isolated yeasts belonged to the Candida, Debaryomyces, and Rhodotorula genera and salt tolerant species were dominant as the salt content of the brines exceeded 11%. Among the determined species, Candida oleophila was the most dominant one and it was thought that isolated strains of Candida oleophila may be taken into consideration to be used as starter culture in table olive production.En este estudio, se investigaron las especies de levaduras que intervinieron en la fermentación natural de aceitunas verdes de mesa del sur de Turquía. Las muestras de aceitunas de mesa se prepararon con cultivares de aceitunas regionales y se emplearon métodos tradicionales en la producción. Las levaduras se aislaron de las salmueras de las muestras en la última etapa de fermentación y se identificaron a nivel de especie mediante las secuencias de ADN del dominio D1/D2 de los genes 26S rRNA. Los dominios D1/D2 fueron amplificados por PCR, secuenciados y comparados con las secuencias de referencia depositadas en la base de datos del NCBI. Según los resultados, las levaduras aisladas pertenecen a los géneros Candida, Debaryomyces y Rhodotorula, y las especies tolerantes a la sal fueron dominantes, ya que el contenido de sal de las salmueras superó el 11 %. Entre las especies determinadas, Candida oleophila fue la dominante y se pensó que las cepas aisladas de Candida oleophila podrían tenerse en cuenta para su uso como cultivo iniciador en la producción de aceitunas de mesa

Genotypic identification and technological characterization of lactic acid bacteria isolated from traditional Turkish Kargi tulum cheese

Kargi tulum cheese is an artisanal cheese produced through the spontaneous fermentation of raw milk ripened inside a goat-skin bag. The objective of this study was to characterize the dominant species of natural lactic acid bacteria (LAB) found in Kargi tulum cheese. Some technologically important properties of LAB isolates were also determined. Seven samples of cheese of different levels of ripeness were taken from local producers and 97 isolates were obtained from these samples. Non-spore forming, Gram-positive, catalase- and oxidase-negative isolates were assessed as LAB. Based on genotypic characterization, the dominant LAB were identified as Lactobacillus paracasei (43.3%), Lactobacillus plantarum (23.7%), Enterococcus durans (6.2%), Streptococcus thermophilus (6.2%), Lactobacillus brevis (5.2%), Enterococcus faecium (5.2%), Lactobacillus fermentum (4.1%) and Lactobacillus pentosus (1%). Homofermentative strains such as L. paracasei, L. plantarum, S. thermophilus; E. durans and E. faecium were selected as probable starter cultures. These strains were tolerant to 6.5% salt. They are also characterized by acidification ability (from pH = 6.6 to 4.7 to 6.0, in 6 to 8 h), low proteinase and high peptidase, esterase, esterase-lipase, β-galactosidase and β- glucosidase activities. They also produce diacetyl and H2O2.Key words: Lactic acid bacteria, genotypic characterization, technological characterization, tulum cheese

Biogenic amines formation in Streptococcus thermophilus isolated from home-made natural yogurt

PubMedID: 23265537Twelve different biogenic amines formation in 58 isolates of Streptococcus thermophilus from home-made natural yogurt were investigated in histidine (HDB) and lysine decarboxylase broth (LDB). All S. thermophilus isolates had an ability to produce twelve different biogenic amines in HDB and LDB. Most of the S. thermophilus isolates formed low amounts of histamine (1-50 mg/L) from histidine. Apart from one isolate, S. thermophilus produced tyramine at low (47 isolates) and medium (10 isolates) levels. The amount of each specific biogenic amine produced by S. thermophilus was generally lower than 100 mg L -1. Also, the presence of hdcA gene was investigated using PCR technique and relation between gene and histamine production was conducted in S. thermophilus isolates. This study showed that most of the S. thermophilus isolates have the ability to form biogenic amines, especially histamine, and tyramine, which is an important consideration when selecting strains as starter cultures. © 2012 Elsevier Ltd. All rights reserved