Improve Production of Microbial Cellulose by Acetobacter xylinum
with Addition of Microparticles in Synthetic and Complex Media
under Shaking Culture Conditions
I.I. Muhamad, S. Z. A. Talib, M. Z. Abdullah, M.K. Mahat and K.S. Ho
Bioprocess Engineering Department, Faculty of Chemical Engineering and Natural Resources, Universiti Teknologi Malaysia, 81310 Skudai, Johor.
Abstract
Results & Discussion
Acetobacter xylinum is a type of bacteria that can synthesize cellulose when
grown in a synthetic and complex medium containing glucose. The effect of
microbial cellulose productivity by adding insoluble microparticles (sea sand)
to submerged, shaken Acetobacter xylinum culture run at 100, 120, 160 and
200 rpm was investigated. The optimal conditions for this culture were at pH
5.0, 300°C and 5 days incubation. Both of synthetic and complex media
(sugarcane juice) were used in this study for comparisons. The result shows
that cellulose production in the microparticle-added media was higher than
in the control media at shaking speed 120 rpm, 160rpm and 200 rpm. It is
also found that production of cellulose in the complex media was higher than
in the synthetic media and with lower water content. Furthermore the highest
yield of cellulose was obtained from using shaking speed at 120 rpm in all
cases.
Keywords: Acetobacter xylinum, microbial cellulose, microparticles, synthetic
Table 1. OD550 value of the medium before and after the fermentation process
and complex media
Speed
(rpm)
SM
SM +
MP
CM
CM +
MP
0
0.6230
0.6220
0.7820
0.6140
100
0.502
0.498
2.336
2.388
120
0.443
0.440
2.267
2.256
160
0.492
0.514
2.462
2.409
200
0.512
0.553
2.516
2.445
CM- complex media SM- synthetic media MP- micro particles
Background
120
20
15
Synthetic
10
Synthetic +
Microparticles
Complex
Glucose analysis before fermentation
Incubation for 5 days at 300°C at different shaking speeds
5
100
80
60
Synthetic
40
Synthetic +
Microparticles
Complex
20
Complex +
Microparticles
0
100
120
160
200
100
Shaking Speed (rpm)
Fig. 1. Effects of the added micro particles on
microbial cellulose production in synthetic and
complex media at various shaking speeds
120
160
200
Shaking Speed (rpm)
Fig. 2. Water contents of the cellulose
produce in synthetic and complex media
at various shaking speeds
Findings:
1.
The low cellulose formation was due to the limited glucose content in
the synthetic media. The hydrolysis process of sucrose into glucose
and fructose in the complex media allowed more formation of
cellulose in the medium. Consequently, the glucose content in the
complex media was generally maintained and optimized during the
fermentation.
2.
More cellulose was produced in both media at 120 rpm particularly in
the microparticle-added flasks. However, the effect of adding
microparticles was more obvious in the synthetic medium.
3.
At 100 and 120 rpm the differences of glucose consumption between
microparticles-added medium and control medium is very small. All
glucose available for the cellulose production where no excessive
dissolved oxygen occurs at these shaking speeds to lead glucose
conversion into gluconic acids.
4.
The complex medium produced cellulose with lower water contents
than that of the synthetic medium but not significantly influenced
either by the presence of microparticles or difference in shaking
speeds.
Inoculation with 10%(v/v) of A.xylinum inoculums
Addition of sterile micro particles into each media
Complex +
Microparticles
0
Approach & Methods
Preparation of synthetic and complex media (Son, 2003)
Percentage of Water Content (%)
Percentage of Dry Weight (%)
25
Microbial cellulose produced by Acetobacter species especially Acetobacter
xylinum displays unique properties, including good mechanical strength, high
water absorption capacity, high crystallinity, and an ultra-fine and highly pure fibre
network structure [1]. It is expected to be a new biochemical commodity with
diverse applications, if its mass production process could be improved, especially
via submerged fermentation technology.
To date, the processes for production of microbial cellulose have used static
cultivation methods, with pellicles of microbial cellulose being formed on the
surface of the static culture. However, this requires a large area in which to place
the culture vessel and is impractical for large scale microbial cellulose production
[2]. Therefore an economical mass production system based on shaking culture is
necessary. However in case of high speed of shaking will decrease the cellulose
production. As a way out for this trouble, this research will determine the
influences of adding microparticles in various speed of shaking culture.
In general, a nutritionally rich medium supports good microbial cellulose
production of Acetobacter xylinum. Several authors have reported the production
of microbial cellulose in complex medium. When compared with complex medium,
synthetic medium has many advantages including enhanced process consistency,
better control and monitoring [3]. For comparisons, the study was carried out in
synthetic and complex medium.
Conclusion
Glucose analysis after fermentation
Measuring wet weight and dry weight of cellulose
The production of cellulose by A.xylinum is controlled by the oxygen supply
which depends on shaking speeds. The highest yield was obtained at 120 rpm
of shaking speed. The presence of microparticles could reduce the effect of
excessive dissolved oxygen supply. It was also determined that the production
of cellulose in complex medium was higher than in the synthetic medium and
with lower water content.
References
[1] Klemm, D., Schumann, D., Udhardt, U. and Marsch, S . (2001). Bacteria Synthesis Cellulose – Artificial Blood Vessels for Microsurgery. Progress In Polymer Science, Vol.26 , p.1561 – 1603.
[2] Okiyama, A., Shirae, H., Kano, H. and Yamanaka, S. (1992) . Bacterial cellulose Ι. Two –stages fermentation process for cellulose production by Acetobacter aceti. Food Hydrocolloids. 6. 471-477.
[3] Son, H. J., Kim, H. G., Kim, K. K., Kim, H. S., Kim, Y. G. and Lee, S. J. (2003). Increased production of bacteria cellulose by Acetobacter sp. V6 in synthetic media under shaking culture conditions.
Bioresource Technology. 86. 215 - 219.
Acknowledgement
The authors would like to thank the Research Management Centre, UTM and Bioprocess Engineering Department, UTM for financial support.