Effect of carbon sources on kombucha biotransormation, organic acides production and synthesis of bacterial cellulose

Kombucha je tradicionalni osvježavajući napitak koji se dobiva fermentacijom zaslađenog čaja zahvaljujući snažnom simbiotičkom djelovanju bakterija octene kiseline i kvasaca. U radu su proučavani nastajanje organskih kiselina (octene i glukonske), etanola i bakterijske celuloze (BC) biotransformacijom kombuche u biljnom čaju zaslađenom saharozom i u Hestrin-Schrammovoj hranjivoj podlozi (HS), koja je sadržavala glukozu, etanol i glicerol kao jedine izvore ugljika. Promjene pH vrijednosti bile su posljedica simbiotičke metaboličke aktivnosti kvasaca i bakterija octene kiseline i opadale su s nastajanjem organskih kiselina. Debljina i prinos bakterijske celuloze povećavali su se tijekom vremena fermentacije. Najveći prinos bakterijske celuloze dobiven je u podlozi s glicerolom (2 % vol/vol) i glukozom (20 g/L) i bio je 17 g/g i 14,5 g/g. Nastajanje bakterijske celuloze povećavalo se razmjerno povećanju odnosa površine i dubine hranjive podloge. Dobiveni rezultati ovog istraživanja ukazuju da maksimalni prinos bakterijske celuloze ovisi o mnogo čimbenika koje još treba dodatno optimizirati. Kombucha is a traditional refreshing beverage obtained by the fermentation of sweetened tea with a powerful symbiosis of acetic bacteria and yeasts. The production of organic acids (acetic and gluconic) and bacterial cellulose (BC) by biotransformation of Kombucha, in herbal tea with wild cherry flavour, sweetened with sucrose and Hestrin and Schramm (HS) based media containing glucose, ethanol or glycerol as sole carbon sources, was studied. Changes in pH were related to the symbiotic metabolic activities of yeasts and acetic acid bacteria, and it is decreased by the formation of organic acids. The thickness and yield of bacterial cellulose increased with fermentation time. The highest bacterial cellulose yield was achieved when glycerol (2% v/v) and glucose (20 g/L) (17 g/g and 14.5 g/g, respectively) were used. The bacterial cellulose production increased correspondingly with increased surface area: depth ratio. Findings from this study suggest that the yield of cellulose depends on many factors that need to be optimised to achieve maximum yield.