No abstract

No abstract

Aim: Confirmation of the enzymatic activity of Class A sortase (SrtA) in probiotic strain Lactobacillus acidophilus associated with the adhesion properties. Materials & methods: SrtA from L. acidophilus ATCC 4356 was purified and its enzymatic properties was investigated by site-directed mutagenesis approach and the sensitivity to metal ions was also detected. Results: SrtA of L. acidophilus ATCC4356 can recognize LPxTG and LPxTD sorting motifs. The active sites of SrtA include His137, Cys198 and Arg205. Furthermore, acacetin can increase the activity of SrtA, while phenyl vinyl sulfone could effectively inhibit the activity of SrtA with an IC50 of 143.32 μg/ml. The adhesion ability of L. acidophilus was also decreased resulting from the inhibition of SrtA activity. Conclusion: The unique properties of SrtA of L. acidophilus can provide some insights into the development of high-adhesion Lactobacillus strains in the GI tract.

The use of probiotic starters in the milk fermentation could provide the dairy products with unique flavors, textures and some health benefits. In this research, L. plantarum A3 was identified as a probiotic with good fermentation characters during the texture and flavor formation of yoghurt. The hardness, consistency, viscosity, and viscosity coefficient of the yoghurt were enhanced when fermented with L. plantarum as the higher activity of β-galactosidase and lactate dehydrogenase in the mixed culture condition. The contents of amino acids and volatile organic compounds (VOCs) were found accumulated in L. plantarum fermented yoghurt besides the butanoic acid, acetone. Sensory profiling evaluation with electronic tongue system proved the novel taste of L. plantarum fermented yoghurt were significant different with the former plain yoghurt. Indeed, yoghurt fermentation with L. plantarum A3 indeed has a good quality and nutrition properties compared with the traditional strains and the relationship between the traditional fermentation strains and probiotics still need further investigation to meet the nutrition requirements of varies consumers.