Beijing Scitop Bio-tech Co., Ltd.

In this study, the effect of luxS, a key gene involved in quorum sensing, on the characteristic flavor of yogurt and its molecular mechanisms during the cofermentation of yogurt with engineered probiotics was investigated. The luxS gene overexpression strain was constructed by the homologous recombination technique, and its effect on the expression of population sensing signaling molecules and luxS gene was determined by bioluminescence and quantitative real-time PCR, and finally, headspace solid-phase micro extraction-GC-MS (HS-SPME-GC-MS) and metabolomics were used to determine the mechanism of its effect on the characteristic flavor of yogurt. The results demonstrated that the overexpression strains of Lactobacillus acidophilus CICC 6074-pMG36e-luxS and Lactobacillus helveticus R0052-pMG36e-luxS were successfully constructed. The expression of the luxS gene was upregulated by 2.25-fold and 3.16-fold, respectively. Compared with the wild-type strains, yogurt fermented by the overexpression strains showed a significant increase in AI-2 content, acidity, viable bacterial count, and protein hydrolysis, whereas pH, water-holding capacity, and hardness were significantly reduced. The HS-SPME-GC-MS results revealed the presence of 31 volatile flavor substances in yogurt. Among them, benzaldehyde (almond and burned sugar flavors), 2,4-dimethyl- (almond, cherry, and naphthalene flavors), dibutyl phthalate (a faint aromatic odor), and n-decanoic acid (rancid and fatty notes) were identified as the key differential flavor substances mediated by the luxS gene. Metabolomics results showed that the luxS gene mediates the production of organic acids in yogurt through arginine and proline metabolism, phenylalanine metabolism, and tryptophan metabolism. This study provides a theoretical basis for a deeper understanding of the molecular mechanisms underlying yogurt flavor formation.

Studies have shown that Alzheimer's disease is associated with significant alterations in the gut microbiota. But the effect of probiotics and/or prebiotics on Alzheimer's disease still remains to be explored. The aim of this study was to determine whether Bifidobacterium Lactis Probio-M8 could alleviate Alzheimer's disease pathophysiologies in the APP/PS1 transgenic mouse model.

4-month old APP/PS1 mice were randomly put into two groups and fed with either Probio-M8 or saline water for 45 days. Fecal samples of mice were collected at the beginning and the end of the treatment period to determine the composition of the gut microbiota via 16S ribosomal RNA sequencing technology. The number and size of Aβ plaques in the brain were quantified. In addition, Y maze, novel object recognition and nest building were employed to access cognitive function in the 8-months old APP/PS1 mice at the end of the treatment period.

Our results demonstrated that Probio-M8 reduced Aβ plaque burden in the whole brain and protected against gut microbiota dysbiosis. Furthermore, Probio-M8 could alleviate cognitive impairment in the APP/PS1 mouse.