Biosynthesis of glucuronic acid by means of tea fungus

Abstract

Tea fungus is the symbiosis of several acetic bacteria and some yeasts [1–3]. If tea fungus is cultivated according to the standard recipe on black tea, sweetened with sucrose, it turns this substrate into a refreshing beverage called tea fungus beverage with high nutritive value and medicinal properties. The components of tea fungus beverage are as follows: ethanol, gluconic, L-lactic, acetic acid [3–6], tartaric, succinic, malic, citric, oxalic and pyruvic acid, purines, pigments, lipids and coffeine [7], amino acids and biogenic amines [8], monosaccharides and proteins [1], enzymes [7–9], vitamins of B group and vitamin C [7, 10–11], antibiotically active substances [12, 13], usnic acid [14], carbon(IV)-oxide as well as insufficiently known products of yeasts and bacteria metabolism. Medicinal properties of tea fungus are reviewed in many references, particularely those of Russian authors [2, 12]. In the course of metabolic activities, tea fungus decomposes enzymatically sucrose into glucose and fructose. Yeasts fermented sucrose, glucose and fructose into ethanol. Acetic bacteria turn glucose, beside other acids, into gluconic acid, while fructose is never turned into this acid [15]. One of the possible ways of glucose transformation is also its oxidation into glucuronic acid at C-6, significant due to its detoxifying effects. Glucuronic acid in human liver binds the toxines making them watersoluble and, therefore, easier for elimination. UDP glucuronic acid, which is the active form of glucuronic acid, was detected in some bacteria [16]. Taking into account the fact that metabolic processes in cognate organisms are generally similar, the presence of UDP glucuronic acid is expected in tea fungus bacteria, too. Glucuronic acid is cited as tea fungus metabolite [6, 14], but without quantitative analyses. The aim of this investigation was to find out whether the culture of tea fungus, cultivated in our laboratory, on substrates with different sucrose concentration produces glucuronic acid. The influence of different concentrations of sucrose, i. e. glucose obtained by enzymatically hydrolysed sucrose, on the production of glucuronic acid was studied as it is known that glucose is a precursor in glucuronic acid biosynthesis [17].