Transcriptomic analysis of Lactococcus chungangensis sp. nov. and its potential in cheese making

摘要

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.