Indigo- and indirubin-producing strains of Proteus and Psychrobacter are associated with purple rind defect in a surface-ripened cheese
Indigo- and indirubin-producing strains of Proteus and Psychrobacter are associated with purple rind defect in a surface-ripened cheese
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DOI：
10.1016/j.fm.2018.07.011
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发表时间：
2018-12-01
影响因子：
5.3
通讯作者：
Wolfe, Benjamin E.
中科院分区：
文献类型：
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作者：
Kamelamela, Noelani;Zalesne, Michael;Wolfe, Benjamin E.
表面成熟干酪的外皮具有预期的美学特性，包括独特的颜色，这有助于整体质量和消费者接受度。在小规模的奶酪生产中，经常报告非典型的果皮色素，但这些颜色缺陷的原因在很大程度上是未知的。我们提供了一个潜在的微生物解释一个惊人的紫色表皮缺陷的表面成熟的奶酪。美国的一家奶酪生产商向我们报告了几批带有明显紫色外皮的生牛奶洗皮奶酪。我们从具有紫色果皮缺陷的样品中分离出变形杆菌属物种，但没有从具有典型果皮色素的样品中分离出，这表明该变形杆菌属菌株可能导致缺陷。当提供色氨酸时，靛蓝和靛玉红生物合成途径的前体，分离的变形杆菌菌株分泌紫红色色素。从紫色和正常果皮中分离出的一种嗜冷菌也分泌紫红色色素。使用薄层色谱法和液相色谱-质谱法，我们证实了这些细菌从色氨酸中产生靛蓝和靛玉红，就像在医疗环境中密切相关的细菌在紫尿袋综合征中产生这些化合物一样。有或没有变形杆菌和嗜冷杆菌的实验奶酪社区证实，这些变形菌引起奶酪皮的紫色色素沉着。来自欧洲的另外两种奶酪中的紫色外皮的报告和从其他奶酪外皮中分离的变形杆菌属和嗜冷杆菌属菌株的色素生产的观察表明，紫色外皮缺陷有可能在表面成熟的奶酪中广泛存在。
The rinds of surface-ripened cheeses have expected aesthetic properties, including distinct colors, that contribute to overall quality and consumer acceptance. Atypical rind pigments are frequently reported in small-scale cheese production, but the causes of these color defects are largely unknown. We provide a potential microbial explanation for a striking purple rind defect in a surface-ripened cheese. A cheese producer in the United States reported to us several batches of a raw-milk washed-rind cheese with a distinctly purple rind. We isolated a Proteus species from samples with purple rind defect, but not from samples with typical rind pigments, suggesting that this strain of Proteus could be causing the defect. When provided tryptophan, a precursor in the indigo and indirubin biosynthesis pathway, the isolated strain of Proteus secreted purple-red pigments. A Psychrobacter species isolated from both purple and normal rinds also secreted purple-red pigments. Using thin-layer chromatography and liquid chromatography-mass spectrometry, we confirmed that these bacteria produced indigo and indirubin from tryptophan just as closely related bacteria make these compounds in purple urine bag syndrome in medical settings. Experimental cheese communities with or without Proteus and Psychrobacter confirmed that these Proteobacteria cause purple pigmentation of cheese rinds. Reports of purple rinds in two other cheeses from Europe and the observation of pigment production by Proteus and Psychrobacter strains isolated from other cheese rinds suggest that purple rind defect has the potential to be widespread in surface-ripened cheeses.