Project description:This project aimed to explore the microbial chemical ecology of a consortium derived from a water kefir fermentation through the integration of directed culturomics, compositional metagenomics and the identification of key metabolites with biological potential, through untargeted metabolomics.
Project description:Water kefir is a slightly alcoholic and traditionally fermented beverage, which is prepared from sucrose, water, kefir grains, and dried or fresh fruits (e.g. figs). Lactobacillus (L.) nagelii, L. hordei and Saccharomyces (S.) cerevisiae are predominant and stable lactic acid bacteria and yeasts, respectively, isolated from water kefir consortia. The growth of L. nagelii and L. hordei are improved in the presence of S. cerevisiae. In this work we demonstrate that quantitative comparative proteomics enables the investigation of interactions between LAB and yeast to predict real-time metabolic exchange in water kefir. It revealed 73 differentially expressed (DE) in L. nagelii TMW 1.1827 in the presence of S. cerevisiae. The presence of the yeast induced changes in the changes in the carbohydrate metabolism of L. nagelii and affected reactions involved in NAD+/NADH homeostasis. Furthermore, the DE enzymes involved in amino acid biosynthesis or catabolism predict that S. cerevisiae releases glutamine, histidine, methionine and arginine, which are subsequently used by L. nagelii to ensure its survival in the water kefir consortium. In co-culture with S. cerevisiae, L. nagelii profits from riboflavin, most likely secreted by the yeast. The reaction of L. nagelii to the presence of S. cerevisiae differs from that one of the previously studied L. hordei, which displays 233 differentially expressed proteins, changes in citrate metabolism and an antidromic strategy for NAD+/NADH homeostasis. So far, aggregation promotion factors, i.e. formation of a specific glucan and bifunctional enzymes were only detected in L. hordei.
Project description:This project aimed to explore the microbial chemical ecology of a consortium derived from a water kefir fermentation through the integration of directed culturomics, compositional metagenomics and the identification of key metabolites with biological potential, through untargeted metabolomics.
Project description:We got insights into the B. bifidum PRL2010 genes whose expression resulted to be affected when bacterial cells were cultivated on kefir and kefiran as the unique carbon source.
Project description:We got insights into the B. bifidum PRL2010 genes whose expression resulted to be affected when bacterial cells were cultivated on kefir and kefiran as the unique carbon source. In order to exploit the transcriptome of PRL2010 grown on kefir and hefiran we performed global transcription profiling using PRL2010 microarrays hybridized with cDNA from the RNA samples of B. bifidum PRL2010 cultivated on these substrates. We isolated mRNA from B. bifidum PRL2010 cells collected from a culture of kefir grains and from PRL2010 cultivated on MRS plus kefiran at upon 12 hours following inoculation. Microarray analysis was performed with an oligonucleotide array based on the B. bifidum PRL2010 genome: a total of 8,130 oligonucleotide probes of 60bp in length were designed on 1707 ORFs using eArray5.0 (Agilent Technologies). 5 Oligos were designed for each gene on a 4x44k Agilent Microarrays(Agilent Technologies, Santa Clara, CA, USA). Replicates were distributed on the chip at random, non-adjacent positions.
Project description:This study examines the proteolytic activity of the kefir grains (a combination of bacteria and yeast) on bovine milk proteins. SDS-PAGE analysis reveals substantial digestion of milk proteins by the kefir grains in comparison with control samples. Mass spectrometric analysis reveals that the kefir microorganisms released 609 new peptide fragments and significantly altered the abundance of around 1,500 peptides compared to the controls. These kefir-digested peptides derived from 55 milk proteins. We show that kefir contains 25 previously identified functional peptides with actions including antihypertensive, antimicrobial, opioid and anti-oxidative .