Cellulose precursors biosynthesis

The cellulose pathway branches at G6P where it is metabolized to UGP-glucose (UDPG), the direct precursor of cellulose. The biosynthesis of UDPG from glucose is a two-step enzymatic process involving phosphoglucomutase and UDPG-pyrophosphorylase. 

Valla S, Ertesvag H, Tonouchi N, Fjaervik E (2009) Bacterial cellulose production biosynthesis and applications. In Rehm BH (ed) Microbial production of biopolymers and polymer precursors applications and perspectives. Caister Academic Press (Norfolk) pp 43-77 Watanabe K, Yamanaka S (1995) Effects of oxygen-tension in the gas-phase on production and physical properties of bacterial cellulose formed under static culture conditions. Biosci Biotechnol Biochem 59 65-68... 

The dolichol-linked D-mannosyl, D-glucosyl, and 2-acetamido-2-deoxy-D-glucosyl residues are used in the glycosylation of proteins and in the biosynthesis of D-m an nan.2,35 GlcNAc-PP-Dol may also play a role in the synthesis of glycosaminoglycans. Reaction 4 is the first step in the formation of lipid-linked precursors for cellulose.46... 

The biosynthesis of cellulose is less well understood than that of glycogen or starch. As a major component of the plant cell wall, cellulose must be synthesized from intracellular precursors but deposited and assembled outside the plasma membrane. The enzymatic machinery for initiation, elongation, and export of cellulose chains is more complicated than that needed to syn-... 

The wall material of plant cells is one of their distinguishing characteristics. As a result, lignin, cellulose, and other wall constituents have been studied in many plant tissue cultures. Phenylpropanoids. for example, have been shown lo be precursors of lignin formation in while pine. Set/noiii. lilac, rose, carrot, and geranium tissue cultures. Moreover, the biosynthesis of lignin has been shown to be alTeeted by kinetin. boron, and major elements, such as calcium. 

In 1953, Bemheimer demonstrated that washed, resting cells from Type III Pneumococcus could synthesize Sill in the presence of D-glucose or certain other monosaccharides, Mg , K , P04 , and oxygen. Biosynthesis of the capsular polysaccharides was shown later to depend on the presence of uridine nucleotides. Similar precursors have been implicated in the biosynthesis of cellulose, chitin, /3-d-(1—>3)-glucan, glycogen, and hyaluronic acid. ... 

Carbohydrates are produced by the process of photosynthesis, which uses the energy of sunlight to produce hexoses from COj and HjO.The plants use these hexoses to harvest energy and produce ATP to fuel cellular function and to produce macromolecules, including starch, cellulose, fats, nucleic acids, and proteins. Animals depend on plants as a source of organic carbon. The hexoses are metabolized to generate ATP and are used as precursors for the biosynthesis of carbohydrates, fats, proteins, and nucleic acids. 

The cell as a biosynthesis machine can use cheap carbon sources (waste products) as precursor substrates to produce bacterial polymers. However, the in vitro synthesis of biopolymers requires costly purified key enzymes and precursor molecules such as ATP, coal, coal bolsters, and nucleotide sugars or sugar acids to synthesize polymers such as PHA, cellulose, alginate, and PGA. Consequently, these polymers have limited commercial applicability due to their very high production costs. It is estimated the production of PHB by in vitro synthesis would amount to a cost of around US 286,000 per gram of PHB whereas, bacterial production of PHB was estimated to cost about 0.0025 per gram of PHB, and this is still 5-10 times as expensive to produce as the respective petroleum-based polymers. 

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