Metagenomic analysis of microbial communities in kombucha and the effect of freeze-dried starter culture on biochemical dynamics

Kombucha is a traditional beverage obtained through the fermentation of sweetened green and / or black tea characterized as an acid, slightly sweet and carbonated beverage. Its chemical profile consists in sugars, organic acids and alcohols, vitamins, amino acids, minerals and tea components. Fermentation is performed by symbiotic association of microorganisms known as SCOBY (Symbiotic Colony of Bacteria and Yeast), composed of cellulose, acetic and lactic acid bacteria and yeasts. Cellulose pellicle, synthetized from glucose by a few genera of bacteria, floats in the fermented liquid and it is generated each fermentation batch. The main genera of microorganisms found in Kombucha beverage are Acetobacter, Gluconaccetobacter and Komagataeibacter for bacteria and Zygosaccharomyces, Candida and Hanseniaspora for yeast. Studies have shown kombucha microbiome changes between fermentations due many environmental factors such as temperature, type and concentration of substrates, starter culture, vessels geometry, pH, amount of oxygen and dissolved CO2. Kombucha elaboration process is quite artisanal and properties of final product are never the same. Since the microorganisms play the most important role in kombucha fermentation, the aim of the present study is to analyse one kombucha's microbiome along with its product formation and sensory properties and evaluate the possibility of freezedrying the starter culture in order to optimize the industrial production and guarantee a standardized product for future applications.