Abstract：
Spore-forming bacteria are the most complex group of microbes to eliminate from the dairy production line due to their ability to withstand heat treatment usually used in dairy processing. These ubiquitous microorganisms have ample opportunity for multiple points of entry into the milk chain, creating issues for food quality and safety. Certain spore-formers, namely bacilli and clostridia, are more problematic to the dairy industry due to their possible pathogenicity, growth, and production of metabolites and spoilage enzymes. This research investigated the spore-forming population from raw milk reception at two Norwegian dairy plants through the cheesemaking stages until ripening. Samples were collected over two years and examined by amplicon sequencing in a culture independent manner and after an anaerobic spore-former enrichment step. In addition, a total of 608 isolates from the enriched samples were identified at the genus or species level using MALDI-TOF analysis. Most spore-forming isolates belong to the genera Bacillus or Clostridium, with the latter dominating the enriched MPN tubes of raw milk and bactofugate. Results showed a great variation among the clostridia and bacilli detected in the enriched MPN tubes. However, B. licheniformis and C. tyrobutyricum were identified in all sample types from both plants throughout the 2-year study. In conclusion, our results shed light on the fate of different spore-formers at different processing stages in the cheese production chain, which could facilitate targeted actions to reduce quality problems.
摘要：
孢子形成细菌是从乳品生产线中消除的最复杂的微生物组，因为它们具有承受乳品加工中通常使用的热处理的能力。这些无处不在的微生物有充足的机会进入牛奶链的多个入口点，造成食品质量和安全问题。某些孢子形成者，即杆菌和梭菌,由于它们可能的致病性，对乳制品行业来说更有问题，增长,产生代谢产物和腐败酶。这项研究调查了两家挪威奶制品厂在奶酪制作阶段从原料奶接收到的孢子形成种群，直到成熟。在两年内收集样品，并以独立于培养物的方式并在厌氧孢子形成剂富集步骤后通过扩增子测序进行检查。此外,使用MALDI-TOF分析在属或种水平鉴定了来自富集样品的总共608个分离株.大多数孢子形成分离物属于芽孢杆菌属或梭菌属，后者主导着富含MPN的原料奶和杆菌管。结果表明，在富集的MPN管中检测到的梭菌和杆菌之间存在很大差异。然而,在整个2年的研究中,在来自两种植物的所有样品类型中鉴定了地衣芽孢杆菌和酪丁酸梭菌。总之,我们的结果揭示了奶酪生产链中不同加工阶段不同孢子形成者的命运，这可以促进有针对性的行动，以减少质量问题。
