Civil Engineering Reference
In-Depth Information
Shoda [79] and Bae
et al.
[80] obtained optimal cellulose yields when agar was included
at 0.4%. h e polysaccharide xanthan was reported to yield similar increases in cellulose
production when added to culture grown in an airlit reactor, however when agar and
xanthan were added to static cultures, decreases in cellulose production were observed
[78] . h e inclusion of 0.04% sodium alginate resulted in increased cellulose produc-
tion from
G. xylinus
NUST4.1 in a glucose/sucrose-CSL medium [81]. However, when
Cheng
et al.
[76] included 0.2% and 0.5% sodium alginate, they showed no increase
in cellulose production. It is possible at these higher concentrations, sodium alginate
inhibits cellulose synthesis, which is in accordance with the i ndings of Zhou
et al.
[81] .
Inclusion of other additives such as 1.25% lactate in CSL-fructose medium was
reported by Naritomi
et al.
[82] as increasing cellulose yield, as well as cell growth
in
G. xylinus
subspecies
sucrofermentans
BPR3001A. Lactate at 0.15% with 0.005%
methionine was reported to increase cellulose production in
G. xylinus
subspecies
sucrofermentans
BPR2001 [70]. Pyruvate, ethanol, aldehyde and acetate were also
shown to stimulate cellulose synthesis in this study, but not to the same levels as lac-
tate. Benziman
et al.
[35] investigated polymerization kinetics in
Gluconacetobacter
using the stilbene derivative, Calcol uor White ST. In this experiment, they found that
Calcol uor White ST increased the rate of glucose polymerization into cellulose by
G.
xylinus
ATCC 23769. Toda
et al
. [83] added 2% acetic acid to GPY medium. h ey found
that
G. xylinus
DA produced high levels of cellulose in static culture with this additive,
whereas other strains showed decreased levels of cellulose. When Ca
2 +
was introduced
into the medium used to grow
Acetobacter aceti
subspecies
xylinus
ATCC 23770 at
concentrations between 1 and 7 mmol/L, bacterial cellulose production increased in
static culture [65]. Dudman [66] investigated the addition of acetate, citrate and suc-
cinate to the growth media for
A. acetigenum
EA-I, and determined that these additives
stimulated cellulose production, the most ef ective of which was succinate. However
succinate decreased cellulose synthesis when used as an additive in a dif erent medium.
In a study designed to improve the cellulose production of
G. xylinus
K3, black tea
and green tea media were used. Cellulose production in these media was not as high
as the control HS medium, however when 0.3% green tea was added to an HS-CSL-
mannitol medium, an increase in cellulose yield was observed [57]. Plant stimulators,
caf eine and related xanthenes, were previously added to media to grow
G. xylinus
BF
by Fontana
et al
. [84] . h is group determined that optimal cellulose synthesis occurred
when tea infusion
Camellia sinesis
was added for growth over more than seven days,
and the addition of
Paullinia
cupana
(“guarana”) for shorter growth periods of less than
i ve days. h ese stimulants are only required in small amounts and may therefore be
inexpensive components with which to increase cellulose production [85]. Many addi-
tives mentioned here may stimulate the synthesis of bacterial cellulose, however addi-
tives do not necessarily need to stimulate cellulose synthesis to achieve increased yields.
For example, Vandamme
et al
. [86] completed a study in which the maximized cellulose
production was achieved by the addition of insoluble microparticles. Diatomaceous
earth, silica, sea sand, small glass beads and loam particles were added to culture media,
and resulted in the cellulose yield being tripled from culture without the insoluble par-
ticles in agitated conditions. h ey concluded that this was due to the artii cial creation
of local oxygen-deprived niches around the particle surfaces, and that this favored cel-
lulose production over gluconic acid production.
