Screening, identification, optimization of culture condition and genome analysis of a bacterium with high ACE inhibitory activity

[Background] Lactobacillus is intestinal probiotics with the frequent observation of high angiotensin converting enzyme (ACE) inhibitory activity in its fermented milk. The marine is an optimal source for biological flora, including abundant types of Lactobacillus. [Objective] Lactobacillus resources were distributed in sediments of the Bohai Sea through the results of high-throughput sequencing. In order to exploit the sources for producing ACE inhibitory peptide and increase the ACE inhibitory activity in fermented milk of Lactobacillus, the present study was performed by using Lactobacillus helveticus GY-3 selected from sediments of the Bohai Sea. [Methods] Lactobacillus resources were detected by using high-throughput sequencing in sediments of the Bohai Sea. After the enrichment separation, 16S rRNA gene identification and genome sequencing analysis were then done on the selected strain. We also measured the ACE inhibitory activity of the fermented milk of the selected strain, and optimized the fermentation conditions of the selected strain through orthogonal test. [Results] Lactobacillus helveticus bacterium (GY-3) was identified and high ACE inhibitory activity was detected in its fermented milk. The optimal conditions for producing ACE inhibitory peptides by strain GY-3 are as follows: 37 °C, 3% inoculation, and 1.0% glucose, 0.6% soy peptone, 1.0% yeast extract and 0.04% MnSO_4·4H_2O in skim milk medium. The maximal ACE inhibitory activity could reach up to 79.52%. On the basis of genome sequence data of the bacterium, it was found that the ACE-inhibiting peptide were involved in the protease system, the polypeptide transport system and the peptidase system. [Conclusion] The present study provides a broader source and foundation for the development of lactic acid bacteria that are capable of producing ACE inhibitory peptide. Studying the genome lays a foundation for the study of biological characteristics and mechanism of ACE inhibition activity in the future. Additionally, this study is of great significance for the development of antihypertensive products.