Fermentation of sugared tea with a symbiotic culture of acetic acid bacteria and yeast (tea fungus) yields kombucha tea which is consumed worldwide for its refreshing and beneficial properties on human health. Important progress has been made in the past decade concerning research findings on kombucha tea and reports claiming that drinking kombucha can prevent various types of cancer and cardiovascular diseases, promote liver functions, and stimulate the immune system. Considering the widespread reports on kombucha, we recognized the need to review and update the research conducted in relation to kombucha tea, its products and tea fungus. Existing reports have suggested that the protective effects of kombucha tea are as good as those of black tea, however, more studies on kombucha tea and its composition are needed before final conclusions can be made.

The antioxidant activity of organic extracts of eight fungal species, Ganoderma lucidum, Ganoderma applanatum, Meripilus giganteus, Laetiporus sulphureus, Flammulina velutipes, Coriolus versicolor, Pleurotus ostreatus and Panus tigrinus, was evaluated for free radical (DPPH· and OH·) scavenging capacity and an effect on lipid peroxidation, and the antibacterial activity was tested by the agar well diffusion method. The highest DPPH· scavenging activity was found in the methanol extract of G. applanatum (12.5 μg/mL, 82.80%) and the chloroform extract of G. lucidum (510.2 μg/mL, 69.12%). The same extracts also showed the highest LP inhibition (91.83%, 85.09%) at 500 μg/mL, while the methanol extracts of G. applanatum and L. sulphureus showed the highest scavenging effect on OH· radicals (68.47%, 57.06%, respectively) at 400 μg/mL. A strong antibacterial activity against Gram-positive bacteria was also manifested. The antioxidative potencies correlated generally with the total phenol content (0.19-9.98 mg/g). The HPLC determination showed that the majority of analysed species contained gallic and protocatechic acids. Consequently, these fungi are shown to be potential sources of antioxidative and antibacterial agents.

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