| Summary: | 碩士 === 國立中興大學 === 食品科學系 === 86 === Abstract The kombucha (or tea fungus) is a symbiotic culture
of having acetic acid bacteria and yeasts as two major
microorganisms. The tea fungus is composed of two portions, a
floating cellulose pellicle layer and thesour liquid broth.
Acetic acid, ethanol, and gluconic acid, are the major
components found in the liquid broth. The fermentation is
traditionally carried out by transplanting a previously
cultivated symbiotic culture, accompanied with the product
cellulose, into a freshly prepared sucrose containing black tea
under aerobic conditions for 7-10 days. Until now only little
literature was available on physiology and metabolic pathway of
tea fungus. In this study, we tried to examine the interaction
occurred between the yeast and bacteria, followed by
investigating the influences of using different combinations of
yeast and acetic acid bacteria isolates as starters, and
different compounds added on metabolic activity of the tea
fungus by using pure cultures. In the study of using different
combinations of yeasts and acetic acidbacteria as starters,the
Schizosaccharomyces pombe K-2 was found to be better then Pichia
membranaefaciens YL-01 in the preparation of the tea fungus. The
production of acetic acid was proportional to that of ethanol.
The consumption rate of sucrose was also closely related to the
viable countof yeast in tea fungus. Glucose, instead of
fructose, was preferentially used by the acetic acid bacteria.
The metabolism rate of the microorganismsin the tea fungus by
using pure cultures combination of S. pomb K-2 with Acetobacter
sp. AL-01 and/or Acetobacter sp. AL-02 was higher than that
ofusing traditional one, but production of cellulose was lower.
It was found that presence of chlorella could enhance the
production of acetic acid, ethanol, and gluconic acid in tea
fungus prepared by using pure cultures. The enhancement was
proportional to the concentration of the chlorella, however,
pollen and honey exerted little effect on the production of
majorcomponents of the tea fungus. If the pollen or honey
(without sterilizationby autoclave) was not added until the tea
fungus had fermented for 3 days. This led to the increased
metabolic activities of both yeast and acetic acid bacteria,
especially productions of both acetic acid and ethanol were
markedlyenhanced. However, chlorella exerted little effect on
production of major products of the tea fungus. The tea
fungus was also prepared by using immobilized yeast and acetic
acid bacteria. Both acetic acid and gluconic acid reached their
maximum values (2.3 %) after 15 days, while the ethanol reached
it''s peak value (1.0%) after 9 days. The flavor of tea fungus
prepared by using immobilized cells was much closed to that of
using traditional transplanting cultures.
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