Karakterizacija funkcionalnog napitka od melise (Melissa officinalis L.) dobijenog fiziološkom aktivnošću čajne gljive / Characterization of functional lemon balm (Melissa officinalis L.) beverage obtained by physiological activity of tea fungus

The aim of this study was to investigate functional characteristics of a kombucha beverage from lemon balm (Melissa officinalis L.) tea. Antibacterial activity of kombucha beverages with optimum and higher acidities was tested against bacteria isolated from food and drinking water. The main active component of antibacterial activity was acetic acid, while slight activity of neutralized kombucha and unfermented tea against some test bacteria indicated presence of other antibacterial components. Total phenol concentration in unfermented tea samples, fermentation broths and kombucha beverages from lemon balm and black tea was determined spectrophotometrically whereas qualitative and quantitative concentration of polyphenolic compounds was determined by HPLC method. Antioxidant activity on DPPH and hydroxyl radical in the same samples was determined on an ESR spectrometer. Fermentation broth and kombucha beverage from lemon balm had higher antioxidant activity against both radicals than the samples from black tea. Kombucha beverage from lemon balm with optimum acidity had higher antioxidant activity than unfermented lemon balm tea. The main active components of antioxidant activity were probably rosmarinic acid and quercetin. Antiproliferative activity of lemon balm tea and kombucha was measured by sulforhodamine B colorimetric assay on HeLa (cervix epitheloid carcinoma), HT-29 (colon adenocarcinoma), and MCF-7 (breast adenocarcinoma) cell lines. By applying concentrations higher than 100 g/ml, tested samples did not stimulate proliferation of cell lines. The possibility of simultaneous lactic acid and kombucha fermentation was tested as well. When starter cultures and Lactobacillus spp. isolates were applied, the content of Land D- lactic acid increased during fermentation, although lactic acid bacteria (except L. hilgardii isolated from sour dough) showed low resistance to the conditions during fermentation and beverages storage. Acetic acid bacteria isolated from local tea fungus were identified by PCR method. Two isolates might be Gluconobacter oxydans and one - Gluconacetobacter hansenii