de Freitas Rosangela, Madec Marie-Noelle, Chuat Victoria, Maillard Marie-Bernadette, Mukdsi María C Abeijón, Falentin Hélène, de Carvalho Antonio Fernandes, Valence Florence, Thierry Anne
Departamento de Tecnologia de Alimentos, Universidade Federal de Viçosa, Viçosa, MG Brazil ; INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
INRA, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France ; AGROCAMPUS OUEST, UMR1253 Science et Technologie du Lait et de l'OEuf, 35042 Rennes, France.
Dairy Sci Technol. 2015;95(4):465-477. doi: 10.1007/s13594-015-0229-2. Epub 2015 May 8.
is widely used in Swiss-type cheese manufacture, where it contributes to flavour and eye development. It is currently divided into two subspecies, according to the phenotype for lactose fermentation and nitrate reduction (lac/nit and lac/nit for subsp. and subsp. , respectively). However, the existence of unclassifiable strains (lac/nit and lac/nit) has also been reported. The aim of this study was to revisit the relevance of the subdivision of into subspecies, by confirming the existence of unclassifiable strains. Relevant conditions to test the ability of for lactose fermentation and nitrate reduction were first determined, by using 10 sequenced strains, in which the presence or absence of the lactose and nitrate genomic islands were known. We also determined whether the subdivision based on lac/nit phenotype was related to other phenotypic properties of interest in cheese manufacture, in this case, the production of aroma compounds, analysed by gas chromatography-mass spectrometry, for a total of 28 strains. The results showed that a too short incubation time can lead to false negative for lactose fermentation and nitrate reduction. They confirmed the existence of four lac/nit phenotypes instead of the two expected, thus leading to 13 unclassifiable strains out of the 28 characterized (7 lac/nit and 6 lac/nit). The production of the 15 aroma compounds detected in all cultures varied more within a lac/nit phenotype (up to 20 times) than between them. Taken together, these results demonstrate that the division of into two subspecies does not appear to be relevant.
它广泛应用于瑞士型奶酪的生产中，对风味和气孔形成有贡献。目前，根据乳糖发酵和硝酸盐还原的表型（分别为lac⁺/nit⁺和lac⁻/nit⁻用于亚种和亚种），它被分为两个亚种。然而，也有报道称存在无法分类的菌株（lac⁺/nit⁻和lac⁻/nit⁺）。本研究的目的是通过确认无法分类菌株的存在，重新审视将其细分为亚种的相关性。首先，通过使用10株已测序菌株确定测试其乳糖发酵和硝酸盐还原能力的相关条件，这些菌株中乳糖和硝酸盐基因组岛的存在与否是已知的。我们还确定基于lac/nit表型的细分是否与奶酪生产中其他感兴趣的表型特性相关，在这种情况下，通过气相色谱 - 质谱法分析了总共28株菌株的香气化合物产生情况。结果表明，孵育时间过短会导致乳糖发酵和硝酸盐还原出现假阴性。他们确认存在四种lac/nit表型，而不是预期的两种，因此在28株已表征的菌株中有13株无法分类（7株lac⁺/nit⁻和6株lac⁻/nit⁺）。在所有培养物中检测到的15种香气化合物的产生在一个lac/nit表型内的变化（高达20倍）比在不同表型之间的变化更大。综上所述，这些结果表明将其分为两个亚种似乎并不合理。
