Bifidobacteria possess inhibitory activity against dipeptidyl peptidase-IV.

UNLABELLED: The incretin hormones are extremely rapidly metabolized by the ubiquitous enzyme dipeptidyl peptidase IV (DPP-IV). Therefore, DPP-IV inhibitors which can prolong the incretin effect are the newest and promising drugs for management of type 2 diabetes. In this study, we investigated whether Bifidobacteria colonizing the human gut possess DPP-IV inhibitory activity. Cell-free intracellular extracts of 13 Bifidobacterium strains isolated from breast-fed infant faecal samples were prepared and screened for DPP-IV inhibitory activity, and two Bifidobacterium strains-Bif. longum BBMN68 and Bif. lactis Bb12-were used as reference strains. Most of the strains showed varying levels of DPP-IV inhibitory property (7-27%). Strains of Bifidobacterium adolescentis IF1-11 and Bifidobacterium bifidum IF3-211 showed the greatest DPP-IV inhibitory activity (27 and 25%) as well as good in vitro probiotic properties. This initial finding suggested that new beneficial function of Bifidobacteria is strain-dependent and the strains or their components may have the potential application for management of type 2 diabetes via inhibiting gastrointestinal DPP-IV activity. Further investigations into the isolation and identification of the bioactive components of Bifidobacteria are warranted. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results show that Bifidobacteria isolated from breast-fed infants' faecal samples possess DPP-IV inhibitory activity. Strains of Bifidobacterium bifidum IF3-211 and Bifidobacterium adolescentis IF1-11, which showed excellent DPP-IV inhibitory properties as well as good in vitro probiotic properties, are expected to be beneficial for application as anti-diabetic probiotics.

Identification and partial characterization of lactic acid bacteria isolated from traditional dairy products produced by herders in the western Tianshan Mountains of China.

UNLABELLED: Thirty strains of lactic acid bacteria (LAB) were isolated from herders' traditional dairy products collected from Xinjiang, China. The species Lactobacillus, Lactococcus, Enterococcus, Pediococcus and Leuconostoc were identified by 16S ribosomal RNA gene sequencing analysis and conventional observation. The strains' fermentation characteristics, including milk acidification, proteolysis, autolysis, antimicrobial activity and diacetyl production, were assayed and compared. Strains NL24 and NL31 showed the highest proteolytic activity-2·75 and 2·08 mmol Phe l(-1) milk, respectively. Strains C, NL41, SW2, Z3-11, NL42 and Z2-91 had high autolytic activity. In addition, most of the wild strains produced diacetyl, half of them to high levels. This study provides a clue to LAB biodiversity in traditional dairy foods produced by herders in the western Tianshan Mountains. High-performing strains should be further evaluated for practical application in value-added fermented dairy products. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results reveal a certain variety of lactic acid bacteria (LAB) in traditional dairy products from Xinjiang. Some of the LAB strains, such as Lactobacillus rhamnosus NL24 and Lactobacillus paracasei SW2, possess excellent functional properties and have the potential for application in indigenous fermented dairy products. Performance of the newly isolated strains in cheese or yogurt manufacturing was further evaluated. Application of the high-performing strains to enrich the flavour of fermented dairy products is highly desirable and holds great commercial potential.