Effect of synthetic microbial community on nutraceutical and sensory qualities of kombucha

Abstract

To mass-produce nutritional kombucha with quality consistency, it is necessary to design synthetic microbial community (SMC) starters with clear bacterial compositions. In this study, a three-species SMC, including Acetobacter pasteurianus, Gluconacetobacter xylinus and Zygosaccharomyces bailii, was designed. Acetic acid bacteria (AAB) in SMC produced a higher concentration of organic acids synergistically compared to each strain inoculated alone. Gluconic acid was the most abundant organic acid in kombucha fermented by SMC, which contributed to the pleasant sour taste of the beverage. AAB could also oxidise the alcohol produced by Z. bailii, making kombucha a soft beverage. Total phenol and flavonoid concentrations increased during fermentation, which enhanced the health benefits of kombucha. The sensory evaluation demonstrated tsshat sensory attributes of SMC fermented kombucha were quite similar to those fermented by the symbiotic culture of bacteria and yeast (SCOBY). Therefore, SMC could be utilised in the industrial mass production of kombucha for better quality control and product consistency.

Microbial Dynamics between Yeasts and Acetic Acid Bacteria in Kombucha: Impacts on the Chemical Composition of the Beverage

“…The experimental results obtained in this study confirm the metabolic interplay between yeasts and acetic acid bacteria that has been theorized for kombucha made from sugared black tea [ 17 , 49 , 51 , 52 ]. They highlight, for the first time, the key role of yeasts and their metabolisms in terms of invertase activity and the fermentation capacity, which can differ, depending on yeast strains ( Table 1 ).…”

“…The presence of monosaccharides after 14 days points to the hydrolysis of sucrose in the external medium. This phenomenon has been reported in several studies [17,[42][43][44]. The total acidity increased between +5.7 and +19.3 meq L −1 and induced a drop of pH between −2.05 and −2.64 units, with significant differences between the values (p < 0.05).…”

“…As a result, the metabolism of yeasts directly impacts the flux of available substrates for AAB. Nevertheless, AAB studied in this work were able to grow in sugared black tea without the presence of yeasts to hydrolyze sucrose, similar to the AAB strains used in Wang et al (2020) [17]. From the perspective of the present results and the experimental conditions of the work cited before, the hypothesis of a snowball effect is supported: Initial spontaneous hydrolysis of sucrose in acidic conditions would be amplified by a pH drop resulting from organic acid production by AAB (Figure S3) [67].…”

“…The production of gluconic acid from the oxidation of released glucose between +0.11 and +1.94 g L − 1 was significantly lower with closed IC for all AAB species except A. papayae ( p < 0.05) and could be explained by the limitation of oxygen [ 7 ]. The production of acetic acid between +0.25 and +0.56 g L − 1 without the initial presence of ethanol can be explained through the glycolysis and pyruvate metabolism of AAB [ 44 , 45 , 46 ] and has been reported in the study of Wang et al (2020) [ 17 ]. Succinic acid production occurred between +0.14 and +0.16 g L − 1 for K. saccharivorans monocultures and malic acid production only occurred for Acetobacter sp.…”

“…This study concluded on the positive impact of the addition of fermented medium on AAB growth and also suggested that acetic acid produced by AAB could stimulate the production of ethanol by yeast. A recent study compared an original kombucha consortium with an unknown microbial composition, and a synthetic consortium including purchased isolates of species commonly found in kombucha [ 17 ]. Two AAB species, consisting of Acetobacter pasteurianus and Komagataeibacter xylinus , were used with the yeast species Z. bailii .…”