Konkit Maytiya, Kim Jong-Hwa, Bora Nagamani, Kim Wonyong
Department of Microbiology, Chung-Ang University College of Medicine, Seoul, Republic of Korea 156-756.
Department of Pharmacy, De Montfort University, Leicester, LE1 9BH, United Kingdom.
J Dairy Sci. 2014 Dec;97(12):7363-72. doi: 10.3168/jds.2014-8299. Epub 2014 Oct 11.
Lactococcus lactis has a played a prominent role in food industry from traditional milk fermentations to industrial scale processes. Extensive studies on the biochemical, physiological, and genetic aspects of L. lactis are evident from published literature. Recently, another novel species, Lactococcus chungangensis, was isolated from activated sludge as the sixth member of the genus to be discovered. To date, no study has been conducted to explore the functional aspects of L. chungangensis to identify features similar to those in L. lactis that are relevant to the dairy industry. Hence, the present study was undertaken to identify functional genes relevant to dairy application through comparative transcriptomic analysis of L. chungangensis with L. lactis. In expression microarray data, 415 genes were upregulated and 1,500 were downregulated of the total 1,915 probes analyzed. Interesting findings from this study were the identification of functional genes such as aminohydrolase and S-adenosylmethionine in L. chungangensis, which are useful in flavor production in cheese making. Probing these genes by PCR and analyzing the sequence confirmed the presence of these genes. Phenotypic analysis of these genes was also investigated by growing the strain in different concentrations of skim milk media to confirm the ability of L. chungangensis to degrade casein in milk, which is the major precursor for flavor enhancing compounds. Other adaptive and stress-response genes such as cold shock and heat shock proteins were also revealed. All experimental investigations at the functional level suggest that L. chungangensis possesses some interesting genes which are of commercial significance, especially in cheese production.
从传统的牛奶发酵到工业规模的生产过程，乳酸乳球菌在食品工业中一直发挥着重要作用。已发表的文献充分证明了对乳酸乳球菌的生化、生理和遗传方面进行了广泛研究。最近，另一个新物种——忠川乳酸乳球菌，从活性污泥中分离出来，成为该属被发现的第六个成员。迄今为止，尚未开展任何研究来探索忠川乳酸乳球菌的功能方面，以确定其与乳酸乳球菌中与乳制品行业相关的特征相似之处。因此，本研究旨在通过对忠川乳酸乳球菌和乳酸乳球菌进行比较转录组分析，来鉴定与乳制品应用相关的功能基因。在表达微阵列数据中，在总共分析的1915个探针中，有415个基因上调，1500个基因下调。本研究的有趣发现是在忠川乳酸乳球菌中鉴定出了诸如氨基水解酶和S-腺苷甲硫氨酸等功能基因这些基因在奶酪制作中的风味产生中很有用。通过PCR探测这些基因并分析序列证实了这些基因的存在。还通过在不同浓度的脱脂牛奶培养基中培养该菌株来研究这些基因的表型分析，以确认忠川乳酸乳球菌降解牛奶中酪蛋白的能力，酪蛋白是风味增强化合物的主要前体。还发现了其他适应性和应激反应基因，如冷休克蛋白和热休克蛋白。在功能水平上的所有实验研究表明，忠川乳酸乳球菌拥有一些具有商业意义的有趣基因，尤其是在奶酪生产中。
