Civil Engineering Reference
In-Depth Information
In an attempt to i nd a cheap carbon source, some groups have used molasses instead
of the other monosaccharides and disaccharides described. However the inclusion of
molasses as a carbon source has been shown to produce mixed results in terms of
cellulose yield. Sugar cane molasses was substituted as the carbon source in an HS
medium in a study by Keshk and Sameshima [61] using six strains of
G. xylinus
. All
strains showed an increased level of cellulose production in the sugar cane molasses
media, compared to glucose as the carbon source. Premjet
et al.
[62] coni rmed these
i ndings and aimed to determine the essential ingredient of the sugar cane molasses
using
G. xylinus
ATCC 10245. By adding various components to media containing
dif erent combinations of carbon sources, they found that the black color substance
component was the most ef ective component of sugar cane molasses in increasing the
production of cellulose.
Bae and Shoda [63] attempted to improve the production of bacterial cellulose
using molasses as the carbon source, but treated the molasses to remove the heavy
metals and minerals which can inhibit microbial growth. h ey applied a H
2
SO
4
-heat
treatment to the molasses before adding it to their CSL medium (in the place of
fructose). h ey reported that in CSL-treated molasses medium,
G. xylinus
BPR2001
cellulose production was less than in CSL-fructose medium (but higher than the
untreated molasses medium). El-Saied
et al.
[54] investigated several dif erent types
of media, including media using the cost ef ective H
2
SO
4
-heat-treated molasses. h ey
reported that when molasses was substituted for glucose in a CSL medium, a slight
increase in cellulose production occurred. However, when molasses was used instead
of mannitol in another medium, slightly lower levels of cellulose were produced. In
accordance with the results of Bae and Shoda [63], the H
2
SO
4
-heat treatment of
molasses increased the cellulose produced over the untreated molasses. h ey also
determined that the optimal concentration of molasses was 17% [54]. Jung
et al.
[64]
used two dif erent methods to treat the molasses, by an H
2
SO
4
and a Ca
3
(PO
4
)
2
treat-
ment method. h ey found that the Ca
3
(PO
4
)
2
treatment method was more ef ective
in terms of producing cellulose, and that both methods were more ef ective than
untreated molasses. h ey also showed that their CSL-molasses medium resulted in
higher cellulose levels than complex media with dif erent carbon sources.
Hong and Qiu [65] have reported using hydrolyzate of konjac powder, produced
from the plant
Amorphophallus rivieri Durieu
, as an alternative carbon source in a
medium containing 0.5% yeast extract and 0.3% tryptone. h ey found that using the
hydrolyzates instead of glucose, mannose and a glucose-mannose mixture as the carbon
source resulted in three, six and i ve times higher cellulose production, respectively.
Many dif erent carbon sources have been investigated, with many dif erences reported
regarding which carbon source provides the highest level of cellulose. However, the
sources that are routinely reported as producing high levels of bacterial cellulose are
glucose, fructose, sucrose and mannitol. It may be that these dif erences occur due to
the dif erent strains being used, or perhaps due to experimental error. It is apparent that
other strains should be examined to determine what their optimal carbon sources are.
Other conditions such as nitrogen sources, additives and cultivation conditions are also
likely to impact the levels of cellulose produced.
