Civil Engineering Reference
In-Depth Information
is preferable for cellulose production. Alternatively it has been reported that 8% CSL is
the optimal concentration for cellulose production [54].
CSL-fructose medium consists of many components [45], however it seems that CSL
confers an increase in the amount of cellulose produced simply by being substituted
for other nitrogen sources in other media. It is likely due to its complex nature and
inclusion of proteins, peptides and amino acids, that CSL may strengthen the buf ering
capacity [71], which together with its low cost makes this nitrogen source a favorable
option for cellulose production.
4.2.2.3.4 Additives
While there are some nutrients required to be included in the media for bacterial cell
growth (such as carbon and nitrogen sources), there are additional supplements that
can be included. h ese additives are not essential for cell growth, and therefore cel-
lulose production, however there are a variety of additives that have been found to
stimulate cellulose production. For example, the use of ethanol as a sole carbon source
in media has been shown to be inef ective. However when ethanol is included with a
suitable carbon source such as glucose, it has been shown, in some cases, to increase
cellulose production [36, 66, 68, 72, 73]. h e inclusion of 1.4% ethanol increased cellu-
lose production approximately four-fold in
Gluconacetobacter
A9 [68] in an optimized
medium. Ethanol added at 1.0% to a fructose-based medium increased cellulose pro-
duction in
G. xylinus
subspecies
sucrofermentans
BPR3001A [72] . h e same concentra-
tion of ethanol was reported to increase cellulose production in
G. xylinus
E
25
[36] and
G. hansenii
PJK [73], where they reported that the ethanol actually decreased
G. han-
senii
cell growth, but also prevented the accumulation of the cellulose non-producing
mutants that can arise in agitated culture [32]. However, Dudman reported that ethanol
had no stimulatory ef ect on cellulose production but did increase cell growth under
static conditions [66].
Lignosulfonate has been used at a concentration of 1% to stimulate cellulose synthesis
[74]. Keshk and Sameshima [74] found decreased levels of gluconic acid and concluded
that this decrease was responsible for the increase in cellulose yield. However, the same
researchers found no signii cant dif erence in cellulose synthesis with the addition of
lignosulfonate in a sugar cane molasses medium [61]. Premjet
et al.
[75] reported that
culture media containing high molecular weight lignosulfonate showed increased cel-
lulose yields over the low molecular weight fraction and the whole “SANPEARL CP”
commercial sulphite pulping waste fraction powder. At er investigating the ef ect of a
range of additives on the cellulose production in
G. xylinus
ATCC 700178, Cheng
et
al.
[76] concluded that the addition of carboxymethylcellulose (CMC) to CSL-fructose
medium led to the highest amount of bacterial cellulose among the tested conditions.
Contradictory results were published by Tantratian
et al.
[77], who reported that the
addition of CMC decreased cellulose production, and Chao
et al.
[78] reported that
CMC did not enhance cellulose production. Cheng
et al.
[76] also reported that the
addition of agar produced higher levels of cellulose than the control.
Chao
et al.
[78] demonstrated the impact of agar, included at 0.1% in CSL-fructose
medium. Cellulose production in
G. xylinus
subspecies
sucrofermentans
BPR2001 was
increased in the presence of agar when grown in an airlit reactor. Similarly, Bae and
