Transformation time course
The capacity of the experimental organism to transform
GL proved to be markedly affected by transformation
period (Figure 5). Consumption of GL and the total
bioconversion efficiencies were increased with the
increase of the incubation period. Maximal yield of GA
(65%) was obtained after 96 h of incubation, with an
obvious decline thereafter. However, the highest yield of
3-oxo-GA (23.43%) was recorded after 72 h. Moreover,
the maximal total conversion value (86.78%) was
achieved after 96 h with consumption of about 90% of the
added GL. During the different phases of the
transformation process, GA was proved to be the major
product. Hattori et al. (1985) reported that, GL was
transformed into three metabolites (GA, 3-epi-GA, 3-oxo-
GA) by human intestinal flora. The reaction seems to
include hydrolysis of GL to GA and glucuronic acid and
reversible transformation of GA to 3-epi-GA via a
metabolic intermediate (3-oxo-GA) by the intestinal flora.
They also demonstrated that, GL could not be converted
to the three metabolites mentioned above by the action of
a single species of bacterium but could be converted by
the cooperative action of bacteria responsible for different
steps of the metabolic pathways (Hattori et al. 1985). A
fairly large number of bacteria showed β-glucuronidase
activity to hydrolyze GL to GA, while a moderate number
of the bacteria had activity to reduce 3-oxo-GA to either
GA or 3-epi-GA (Hattori et al. 1983; 1985; Akao 1997).
Transformation time course
The capacity of the experimental organism to transform
GL proved to be markedly affected by transformation
period (Figure 5). Consumption of GL and the total
bioconversion efficiencies were increased with the
increase of the incubation period. Maximal yield of GA
(65%) was obtained after 96 h of incubation, with an
obvious decline thereafter. However, the highest yield of
3-oxo-GA (23.43%) was recorded after 72 h. Moreover,
the maximal total conversion value (86.78%) was
achieved after 96 h with consumption of about 90% of the
added GL. During the different phases of the
transformation process, GA was proved to be the major
product. Hattori et al. (1985) reported that, GL was
transformed into three metabolites (GA, 3-epi-GA, 3-oxo-
GA) by human intestinal flora. The reaction seems to
include hydrolysis of GL to GA and glucuronic acid and
reversible transformation of GA to 3-epi-GA via a
metabolic intermediate (3-oxo-GA) by the intestinal flora.
They also demonstrated that, GL could not be converted
to the three metabolites mentioned above by the action of
a single species of bacterium but could be converted by
the cooperative action of bacteria responsible for different
steps of the metabolic pathways (Hattori et al. 1985). A
fairly large number of bacteria showed β-glucuronidase
activity to hydrolyze GL to GA, while a moderate number
of the bacteria had activity to reduce 3-oxo-GA to either
GA or 3-epi-GA (Hattori et al. 1983; 1985; Akao 1997).
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