1. Bacteria from the species of Aerobacter, Acetobacter,
Achromobacter, Agrobacterium, Alacaligenes, Azotobacter,
Pseudomonas, Rhizobium and Sarcina synthesize cellulose.
Only the Acetobacter species produce enough cellulose to justify
commercial interest. The most extensively studied member of the
Acetobacter species is A. xylinus, formerly known as A. xylinum.
SEM micrograph of the wet structure of microbial cellulose.

2. Bacterial cellulose x 20000 (a) and plant cellulose x 200 (b).
Acetobacter are of particular importance commercially, because:
- they are used in the production of vinegar (intentionally converting the
ethanol in the wine to acetic acid)
- they can destroy wine which it infects by producing excessive amounts
of acetic acid or ethyl acetate
- they are used to intentionally acidify beer during long maturation
periods
Advantages Over Plant Cellulose
Some advantages of microbial cellulose over plant cellulose include:
Finer structure
No hemicellulose or lignin need to be removed
Longer fiber length: much stronger
Can be grown to virtually any shape
Disadvantages for Commercial Use
Some issues that prevented larger scale commerciaization so far include:
High price (about 100 x more than plant cellulose)
Because of high priced substrates: sugars
Low volumetric yields
Lack of large scale production capacity
Potential Future Improvements a b
Bacterial cellulose x (a) and plant cellulose x 200 (b).
Plant cellulose and bacterial cellulose have the same chemical
structure, but different physical and chemical properties.
Bacterial cellulose is produced by an acetic acid-producing bacterium,
Acetobacter xylinum.
The diameter of biocellulose is about 1/100 of that of plant cellulose
and Young's modulus of biocellulose is almost equivalent to that of
aluminum. Therefore, biocellulose is expected to be a new
biodegradable biopolymer.

3. Cellulose is found in plants as microfibrils (2-20 nm diameter and 100 -
nm long). These form the structurally strong framework in the
cell walls. Celluloseis mostly prepared from wood pulp
Structural unit
Cellulose is a linear polymer of β-(1 4)-D-glucopyranose units in 4C1
conformation. The fully equatorial conformation of β-linked
glucopyranose residues stabilizes the chair structure, minimizing its
flexibility (e.g. relative to the slightly more flexible α-linked
glucopyranose residues in amylose).
Cellulose
cellulose, since it is not bonded to other substances, is not
chemically modified after isolation from wood
a-cellulose
wood cellulose that is insoluble in strong NaOH (17.5%)
b-cellulose
soluble in strong NaOH, but precipitates when neutralized
g-cellulose
material remaining soluble after neutralization
Direct Isolation Methods
nitric acid in ethanol
acidified acetyl-acetone and dioxane
Cl2 and NO2 in DMSO or SO2 in DMSO

4. Cellulose Biosynthetic Pathway in Acetobacter xylinum
Glc, glucose; G6P, glucose-6-phosphate; G1P, glucose-1-phosphate;
PGA,phosphogluconic acid; Frc, fructose; F1P, fructose-1-phosphate; FDP, fructose-
1,6- phosglucomutase; UGP, UDP-glucose pyrophosphorylase; PGH,
phosphoglucomutase; UGP, UDP-glucose pyrophorylase; G6PD, glucose-6-
phosphate dehy-drogenase; PGI, phosphoglucose isomerase; FHK, fructose
hexokinase; 1 PFk,fructose-1-phosphate kinase; FBP, fructose bis-phosphatase;
PTS, phosphotransferase system; EMP, Embden-Myerhoff pathway.
The predicted pathway of cellulose synthesis and secretion when glucose is taken into
Gluconacetobactor xylinum from the outside of the cell.
( )

5. Future aspects
Preservation of forest resources is essential to prevent global warming
because the increase in CO2 concentration can be stopped only by the
absorption of CO2 by plants and trees.
However, the use of trees for the production of paper and construction
materials has continuously depleated forest resources.
Bacterial cellulose is the only alternative for plant cellulose because
bacteria produce bacterial cellulose in a few days, while trees need more
than 30 years to realize full growth. In this respect, bacterial cellulose is
the key material for preventing global warming and preservation of the
nature.