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for A.xylinum which used in prior researches. Then choose the suitable one for those experiments which
some adjustments. The type of bioreactor chosen is Stirred Tank Reactor with gate and turbin-rushton
agitator type. These activities followed by engineering of the bioreactor in line with the experiments condition
which will be used.
Another activity parallel to the design and engineering are adaptation of static culture to the
dynamic culture of A.xylinum. This microorganism formerly grew and maintained in a static culture. But
to be used in the experiments, it must be adapted to dynamic culture. This experiments run on stirred tank
reactor to increase the productivity of A.xylinum.
Theory 3.1 Fibrillation in Papermaking
Microibrillation is an effort of paper industry to increase the strength of paper. After reining, the body
of the ibers will collapse, the surface of the ibers will delaminated and emerge ibrils. Basically ibrillation
is delamination of the iber cell wall. These illustrated in Fig. 1.
Figure 1. Microibrillation in Fiber Surface The Figure 2, shows principally how nanoibrillation
proceed in bacteria culture medium. Plant ibers insert to culture media, sterilize, and inoculate by cellulose
producing bacteria.
Figure 2. Nanoibrillation in Fiber Surface The mechanism of micro and nanoibrillation is
different. Microibrillation is done mechanically, but the nanoibrillation is done biologically. Fibrils in
nanoibrillation do not come from delamination of iber cell wall, but growth on the surface of the ibers
as a result of microorganism activities. There is no iber collapse. These ibrils growth in line with the
productivity of microorganism and called bacterial cellulose. The chemical formula of this cellulose is
the same as plant cellulose ibers but different in term of chemical and physical properties Yoshinaga et al.,
1997.
3.2 Reactor Types for Acetobacter xylinum
Cellulose extracellular can be synthesized by the bacteria of the genus Acetobacter, Rhizobium,
Agrobacterium, Aerobacter, Achromobacter, Azotobacter, Rhizobium, Sarcina, Salmonella, and
Escherichia Ross et al., 1991. It can be produced in static or dynamic condition. Production method can
inluence the quantity and quality of cellulose product. Bacterial cellulose produced by these methods is
not in a pure condition but contain some impurities such as medium components and cells of Acetobacter
xylinum. Puriication is needed to reduce the amount of impurities Yamanaka et al, 1989. In static method
bacterial cellulose produced in a gelatinous sheet, but in dynamic method agitated bacterial cellulose
will accumulated as a suspension. Dynamic method is suitable for industrial and commercial application.
Bacterial cellulose can be applied in any kind of industry such as paper, textile, food, cosmetics, and
medicines Bielecki et al., 2001 and used as a resource of cellulose alternative which high biodegradable
properties Vandamme et al., 1998.
The extent of bacterial cellulose production depend on culture condition, including incubation
method, source of nitrogen and carbon, acidity pH, temperature, and dissolved oxygen. Some researchers
have been done to optimize bacterial cellulose production. Glucose is well known as a main carbon
source for producing bacterial cellulose. The others sources can also be used such as monosaccharide
carbon and organic acid Hextrin and Schramn, 1954. Growth media for bacterial cellulose production
should contain carbon, nitrogen, phosphor, sulfur, potassium and magnesium salts Chawla et al., 2009.
Cellulose production depends on the amount of glucose consumption. Production cost of bacterial
cellulose is proportional to chemicals usage which will be costly compared to other organic commercial
products Shoda dan Sugano, 2005.
Bioreactor is an equipment to provide suitable environment so microorganism biologically active.
Some types of bioreactor usually used for bacterial cellulose production are stirred tank, air lift, rotary,
and bubble column, see the following igure.
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Ideal design of bioreactor can increase the productivity of bacterial cellulose synthesis. Many
method and design of bioreactor have previously investigated Watanabe et al, 1998. Some of those
methods are potentially applied in commercial and economical of bacterial cellulose production. In
dynamic media with agitation culture, high cellulose production needs high oxygen transfer rate means
big motor and energy is required. The inluenced of agitator coniguration to oxygen transfer rate have
been investigated Matsuoka et al., 1996. From those investigations it was concluded that stirred tank
reactor using gate with turbine impellers or maxblend agitator type are the best one Kouda et al., 1997.
Results and Discussions 4.1 Design and Engineering of Bioreactor
From the literature review, the reactor type suitable for bacterial cellulose production was chosen. It was
a Stirred Tank Reactor with gate and turbin-rushton agitator type. The dimension of the reactor is about
100 L volume and height 750 mm. All the size component of the reactor depends on this dimension.
The following igure 5 shows the design of the reactor. The bioreactor equipped with temperature control
of the culture media and rotation control of the agitator. A heater element is jacketed to the reactor.
Temperature can be varied from 30 to 120 °C and the sterilization methods up to 100 °C is done by this way.
The agitation speed can be varied from laminar to turbulent type of growth media.
4.2 Surface Modiication of Fibers
