0000000000760823
AUTHOR
Thierry Tran
Polyphenols in kombucha: Metabolomic analysis of biotransformations during fermentation
Kombucha is a non-alcoholic beverage made of sugared tea that is transformed by a symbiotic consortium of yeasts and bacteria. This beverage is increasingly produced at industrial scale, but its quality standards remain to be defined. Metabolomics analysis was carried out using FT-ICR-MS (Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry) to understand the chemical transformations induced by the production phases and the type of tea on the non-volatile compounds of kombucha.
Microbial Dynamics between Yeasts and Acetic Acid Bacteria in Kombucha: Impacts on the Chemical Composition of the Beverage.
Kombucha is a traditional low-alcoholic beverage made from sugared tea and transformed by a complex microbial consortium including yeasts and acetic acid bacteria (AAB). To study the microbial interactions and their impact on the chemical composition of the beverage, an experimental design with nine couples associating one yeast strain and one AAB strain isolated from original black tea kombucha was set up. Three yeast strains belonging to the genera Brettanomyces, Hanseniaspora, and Saccharomyces and three strains of Acetobacter and Komagataeibacter species were chosen. Monocultures in sugared tea were analyzed to determine their individual microbial behaviors. Then, cultivation of the ori…
Study of microbial dynamics for the control of Kombucha production
Kombucha is a fermented beverage obtained from the transformation of sugared tea infusion through the activity of a consortium of yeasts and bacteria, during which a cellulosic biofilm is formed. The study of microbial interaction that occur in this matrix aims at improving the control over the production process at industrial scale. The methodology used in this work is mainly based on the isolation and selection of yeasts and acetic acid bacteria from a determined kombucha consortium. The selected microorganisms are then used to inoculate monocultures and cocultures in sugared black tea. Different parameters were followed at the microbiological level (population counts, composition in gene…
Effect of high hydrostatic pressure on extraction of B-phycoerythrin from Porphyridium cruentum: Use of confocal microscopy and image processing
International audience; The aim of the study was to extract B-phycoerythrin from Porphyridium cruentum while preserving its structure. The high hydrostatic pressure treatments were chosen as extraction technology. Different methods have been used to observe the effects of the treatment: spectrophotometry and confocal laser scanning microscopy followed by image processing analysis. Image processing led to the generation of masks used for the identification of three clusters: intra, extra and intercellular. All methods showed that high hydrostatic pressure treatments between 50 and 500 MPa failed to extract B-phycoerythrin from Porphyridium cruentum cells. The fluorescence emission was negati…
Polyphenols in kombucha: impact of infusion time on extraction and investigation of their behavior during "fermentation"
Kombucha is a non-alcoholic beverage made of sugared tea that is transformed by a symbiotic consortium of yeasts and bacteria. Polyphenols are expected to be responsible of several health benefits attributed to kombucha consumption, among other metabolites. Evidence point at an enhancement of tea polyphenol bioactivity during kombucha elaboration. This study investigated the impact of tea infusion time and of kombucha "fermentation", on the tea polyphenols and the color. Most of the present experiments have been carried out during a 3 rd year Bachelor training by Shane Fennell from Carlow Institute of Technology (Ireland).
Microbiological and technological parameters impacting the chemical composition and sensory quality of kombucha
International audience; Kombucha is a beverage made from sugared tea transformed by yeasts and acetic acid bacteria. Being originally homemade, it has become an industrially produced soft drink whose quality standards are poorly defined and whose production process is still not fully controlled. Based on current knowledge in beverages, links between kombucha's chemical composition and sensorial compounds are drawn. Macromolecules create turbidity, whereas uncharacterized tea pigments derivatives participate in the color. Residual sugars bring sweetness and organic acids produced by acetic acid bacteria form its characteristic sour taste. Acetic acid is also part of its aroma profile, althou…
3-Methylation alters excited state decay in photoionised uracil.
UV and VUV-induced processes in DNA/RNA nucleobases are central to understand photo-damaging and photo-protecting mechanisms in our genetic material. Here we model the events following photoionisation and electronic excitation in uracil, methylated in the 1′ and 3′ positions, using the correlated XMS-CASPT2 method. We compare our results against those for uracil and 5-methyl-uracil (thymine) previously published. We find 3-methylation, an epigenetic modification in non-negligible amounts, shows the largest differences in photoionised decay of all three derivatives studied compared to uracil itself. At the S0 minimum, 3-methyl-uracil (3mUra) shows almost degenerate excited cation states. Upo…
Shedding Light on the Formation and Structure of Kombucha Biofilm Using Two-Photon Fluorescence Microscopy
Kombucha pellicles are often used as inoculum to produce this beverage and have become a signature feature. This cellulosic biofilm produced by acetic acid bacteria (AAB) involves yeasts, which are also part of the kombucha consortia. The role of microbial interactions in thede novoformation and structure of kombucha pellicles was investigated during the 3 days following inoculation, using two-photon microscopy coupled with fluorescent staining. Aggregated yeast cells appear to serve as scaffolding to which bacterial cellulose accumulates. This initial foundation leads to a layered structure characterized by a top cellulose-rich layer and a biomass-rich sublayer. This sublayer is expected t…