Microbial cellulose is a form of cellulose

Cellulose

Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand β linked D-glucose units....

 that is produced by bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. It is widely used in the traditional Filipino dessert Nata de coco

Nata de coco

Nata de coco is a chewy, translucent, jelly-like food product produced by the fermentation of coconut water, which gels through the production of microbial cellulose by Acetobacter xylinus. Nata de coco is most commonly sweetened as a candy or dessert, and can accompany many things including...

. Microbial cellulose was first confirmed as cellulose in 1886.

Production

Bacteria from the genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Aerobacter, Acetobacter

Acetobacter

Acetobacter is a genus of acetic acid bacteria characterized by the ability to convert ethanol to acetic acid in the presence of oxygen. There are several species within this genus, and there are other bacteria capable of forming acetic acid under various conditions; but all of the Acetobacter are...

, Achromobacter

Achromobacter

The Achromobacter are a genus of bacteria, included in the order Burkholderiales. The cells are straight rods and are motile by using 1 – 20 peritrichous flagella. They are strictly aerobic and are found in water and soils....

, Agrobacterium

Agrobacterium

Agrobacterium is a genus of Gram-negative bacteria established by H. J. Conn that uses horizontal gene transfer to cause tumors in plants. Agrobacterium tumefaciens is the most commonly studied species in this genus...

, Alacaligenes, Azotobacter

Azotobacter

Azotobacter is a genus of usually motile, oval or spherical bacteria that form thick-walled cysts and may produce large quantities of capsular slime. They are aerobic, free-living soil microbes which play an important role in the nitrogen cycle in nature, binding atmospheric nitrogen, which is...

, Pseudomonas

Pseudomonas

Pseudomonas is a genus of gammaproteobacteria, belonging to the family Pseudomonadaceae containing 191 validly described species.Recently, 16S rRNA sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the...

, Rhizobium

Rhizobium

Rhizobium is a genus of Gram-negative soil bacteria that fix nitrogen. Rhizobium forms an endosymbiotic nitrogen fixing association with roots of legumes and Parasponia....

and Sarcina

Sarcina (genus)

Sarcina is a genus of Gram-positive cocci bacteria in the family Clostridiaceae. A synthesizer of microbial cellulose, they have a cuboidal cell arrangement...

synthesize cellulose. However, only the Acetobacter species produce enough cellulose to justify commercial interest. The most extensively studied member of the Acetobacter species is Gluconacetobacter xylinus, formerly known as Acetobacter xylinum.

G.xylinus extrudes glucan chains from pores into the growth medium. These aggregate into microfibrils, which bundle to form microbial cellulose ribbons. Various kinds of sugars are used as substrate. Production occurs mostly at the interface of liquid and air.

Differences with plant cellulose

Some advantages of microbial cellulose over plant cellulose include:

• Finer and more intricate structure
• No hemicellulose
  Hemicellulose
  A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
  
   or lignin
  Lignin
  Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
  
   need to be removed
• Longer fiber length: much stronger
• Can be grown to virtually any shape
• Can be produced on a variety of substrates
• The formula of the media used and the strain of Acetobacter xylinum will determine the quality of the pellicle
• More absorbent per unit volume

Disadvantages for commercial use

Some issues that have prevented large scale commercialization 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
• Timely expansion and maintenance of the cell culture for production

Functions

One continuing mystery surrounding microbial cellulose is its exact biological function. A. xylinus recently renamed as "Gluconacetobacter xylinus" is a successful and prevalent bacterium in nature, frequently finding a home in rotting fruits and sweetened liquids. The most familiar form of microbial cellulose is that of a pellicle on the top of a static cultured growth media. It has thus been hypothesized that cellulose acts as a floatation device bringing the bacteria to the oxygen rich air-media interface. This hypothesis has largely been discredited by experiments conducted on submerged oxygen-permeable silicone tubes that show cellulose grows well submerged if enough oxygen is present. Others suspect that cellulose is used to immobilize the bacteria in an attempt to keep it near the food source; or as a form of protection against ultraviolet light.

Medical

Microbial cellulose is biocompatible and non-toxic making it a good candidate material for medical applications. So far it has found a commercial role in some wound dressings

Dressing (medical)

A dressing is an adjunct used by a person for application to a wound to promote healing and/or prevent further harm. A dressing is designed to be in direct contact with the wound, which makes it different from a bandage, which is primarily used to hold a dressing in place...

. There is on-going research to evaluate a possible role for bacterial cellulose in the following applications:

• Scaffolds for tissue engineering
  Tissue engineering
  Tissue engineering is the use of a combination of cells, engineering and materials methods, and suitable biochemical and physio-chemical factors to improve or replace biological functions...
  
  
• Synthetic dura mater
  Dura mater
  The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
  
  
• Bladder neck suspension
• Soft tissue replacement
• Artificial blood vessels

Non medical

• Matrix for electronic paper
• High strength paper
• Diet foods
• Desserts: nata de coco
  Nata de coco
  Nata de coco is a chewy, translucent, jelly-like food product produced by the fermentation of coconut water, which gels through the production of microbial cellulose by Acetobacter xylinus. Nata de coco is most commonly sweetened as a candy or dessert, and can accompany many things including...
  
  
• Substrates for OLEDs
• Sony
  Sony
  , commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
  
  has use microbial cellulose as an acoustic membrane in high-end earphones
• It has a proposed use as a gloss surface finish in magazines