Kombucha tea fermentation and its antimicrobial activity

Kombucha je odavno poznati osvježavajući napitak dobiven fermentacijom čaja, uz dodatak šećera i simbiotički združene kulture bakterija octene kiseline i kvasaca. Ovaj se napitak stoljećima intenzivno konzumira diljem cijelog svijeta zbog svojih profilaktičkih i terapeutskih svojstava. U ovom su radu pripremljene infuzije crnog, zelenog, bijelog i voćnog čaja (5 g/L), zaslađene sa 70 g/L saharoze, te fermentirane pomoću kombuche tijekom 35 dana pri 28°C. Uočeno je da su promjene pH vrijednosti bile povezane sa simbiotskim metaboličkim aktivnostima kvasaca i bakterija octene kiseline. Debljina i prinos bakterijske celuloze povećala se tijekom fermentacije. Uočena je antimikrobna aktivnost kombuche na Gram-pozitivne i Gram-negativne bakterije (Streptococcus aureus, Escherichia coli i Salmonella typhimurium), no ne i na kvasac Candida albicans.Kombucha is a traditional refreshing beverage obtained by the fermentation of sugared tea with a powerful symbiosis of acetic bacteria and yeasts. This drink has been extensively consumed for a long time worldwide for its prophylactic and therapeutic properties. In this present study, the tea broths produced with black, green, white and fruit teas (5 g/L) were fermented naturally at 28°C with kombucha over a period of up to 35 days in the presence of 70 g/L sucrose. Changes in pH were related to the symbiotic metabolic activities of yeasts and acetic acid bacteria. The thickness and yield of bacterial cellulose increased with fermentation time. Antimicrobial activities were observed in the fermented samples against the tested Gram-positive and Gram-negative organisms (Streptococcus aureus, Escherichia coli and Salmonella typhimurium), but Candida albicans was not inhibited by kombucha