Data_Sheet_1_Metatranscriptomic Analyses Unravel Dynamic Changes in the Microbial and Metabolic Transcriptional Profiles in Artisanal Austrian Hard-Cheeses During Ripening.pdf

Vorarlberger Bergkäse (VB) is an artisanal Austrian washed-rind hard cheese produced from alpine cows’ raw milk without the addition of ripening cultures. Ripening time is a key factor in VB, as it strongly influences the microbial communities present in the cheeses and the organoleptic properties of the product. In this study, the microbial and metabolic transcriptional profiles in VB rinds at different ripening times were investigated. VB products before (30 days of ripening) and after (90 days of ripening) selling were selected, RNA was extracted and subjected to shotgun metatranscriptomic sequencing. The analysis revealed some of the previously described abundant bacterial taxa of Brevibacterium, Corynebacterium, Halomonas, Psychrobacter, and Staphylococcus to be highly active in VB rinds. Additionally, the investigation of most important metabolic pathways in cheese ripening clearly showed differences in the gene transcription profiles and the active microbiota between the two ripening points investigated. At 30 days of ripening, metabolic events related with the degradation of residual lactose, lactate, citrate, proteolysis, and lipolysis were significantly more transcribed and mainly associated with Staphylococcus. On the other hand, genes involved in the degradation of smaller compounds derived from previous metabolism (i.e., metabolism of free amino acids and fatty acids) were significantly more expressed in VB rinds with 90 of ripening, and mainly associated with Brevibacterium and Corynebacterium. These latter metabolic activities are responsible of the generation of compounds, such as methanethiol and 2,3-butanediol, that are very important for the flavor and aroma characteristics of cheeses. This study shows the dynamic changes in the gene transcriptional profiles associated with energy substrates metabolism and the generation of organoleptic compounds during VB ripening and uncovers bacterial taxa as key drivers of the ripening process. These taxa might be the target for future studies toward an accelerated cheese ripening and the enhancement of its organoleptic properties.

沃拉尔贝格高山奶酪（VB）是一种手工制作的奥地利洗皮硬质奶酪，由未经发酵文化添加的阿尔卑斯奶牛生乳制成。在VB中，成熟时间是一个关键因素，因为它显著影响奶酪中的微生物群落及其产品的感官特性。在本研究中，对VB奶酪皮在不同成熟时间下的微生物和代谢转录组进行了调查。选取了销售前（成熟30天）和销售后（成熟90天）的VB产品，提取RNA并进行枪式宏转录组测序。分析揭示了先前描述的一些丰富细菌类群，如短杆菌属、棒杆菌属、盐杆菌属、嗜冷杆菌属和葡萄球菌属，在VB奶酪皮中活性极高。此外，对奶酪成熟过程中最重要的代谢途径的研究清楚地显示了两个调查成熟点之间基因转录谱和活性微生物群的不同。在30天成熟时，与残留乳糖、乳酸、柠檬酸、蛋白质分解和脂肪分解相关的代谢事件转录显著增加，主要与葡萄球菌相关。另一方面，参与降解先前代谢产生的小分子化合物（即游离氨基酸和脂肪酸的代谢）的基因在90天成熟时的VB奶酪皮中表达显著增加，主要与短杆菌属和棒杆菌属相关。这些后者的代谢活动负责生成如甲硫醇和2,3-丁二醇等重要化合物，这些化合物对奶酪的风味和香气特性至关重要。本研究展示了与能量底物代谢和感官化合物生成相关的基因转录谱在VB成熟过程中的动态变化，并揭示了细菌类群作为成熟过程中的关键驱动因素。这些类群可能成为未来研究加速奶酪成熟和提升其感官特性的目标。