Chitosan producers

Chitosan is not widely present as such in nature and thus cannot be directly extracted from natural resources. Indeed, chitosan is a derivative of natural chitin, the second most abundant polysaccharide in nature after cellulose [2]. Typically, chitosan is obtained by deacetylation of the Ai-acetyl glucosamine units of chitin, generally by hydrolysis under alkali conditions at high temperature. The deacetylation of chitin is rarely complete. When the degree of acetylation falls below the value of 60 mol%, chitin becomes chitosan. In nature, chitin is present in life forms and more particularly in insects and crustaceans where it represents the major component of their exoskeleton. Chitin is also present in the cell wall of some mushrooms [7, 8]. Generally, chitosans produced from mushrooms present a narrow molecular weight distribution compared to chitosan produced from shrimps, and a non-animal source is considered to be safer for biomedical and healthcare uses. 

The physical and mechanical properties of chitosan can be amefiorated by using graft copolymerization and crosslinking. Chitosan forms aldimines and ketimines with aldehydes and ketones, respectively. Upon hydrogenation with simple aldehydes, chitosan produces A-alkyl chitosan [60]. The physicochemical and biological properties [61] as well as conformational structures [62] of chitosan are very effective for biomedical applications. 

Y. Cho, R. Shi, R.B. Borgens, Chitosan produces potent neuroprotection and physiological recovery following traumatic spinal cord injury, J. Exp. Biol. 213 (2010) 1513-1520. 

Paulino et al. (2006) obtained chitin with high purity from silkworm pupa, but the yield of chitin and chitosan were low when compared with the chitin and chitosan produced from aquatic crustacean shells. The lower yield of chitin may be due to the effect of treatment on insect materials with HCl at high temperature (Table 1.1). Therefore, it should be considered that the process of acid demineralization step is to be carried out under mild condition, which can avoid the possibility... 

Davoust, N. and G. Hansson. 1992. Identifying the conditions for development of beneficial mycelium morphology for chitosan-producing Absidia spp. in submersed cultures. Applied Microbiology and Biotechnology 36 618-620. 

The other area of development that would benefit researchers is the availability of several molecular weights of chitin and chitosan produced under the same stringent production criteria. 

Chung, Y.-C., Kuo, C.-L., and Chen, C.-C. 2005. Preparation and important functional properties of water-soluble chitosan produced through Mailard reaction. Bioresour. Technol. 96 1473-1482. 

Some efforts are being made to develop biodegradable plastics based on chitosan, produced from shrimp and crab shells. One company involved in this effort was Aisero Chem-... 

Kaur K, Dattajirao V, Shrivastava V et al (2012) Isolation and characterization of chitosan-producing bacteria from beaches of Chennai, India. Enzyme Res. doi I0.II55/20I2/42I683... 

A.E.C. Fai, T.C.M. Stamford, T.M. Stamford-Arnaud, P.A. Santa-Cruz, M.C.F. Silva, G.M. Campos-Takaki, T.L.M. Stamford, Physico-chemical characteristics and functional properties of chitin and chitosan produced by Mucor circinelloides using yam bean as substrate. Molecules, 16,7143-7154, 2011. 

Chitosan, produced commercially by deacetylation of chitin, is a natural polysaccharide composed of randomly distributed (J-l, 4-linked D-glucosamine and N-acetyl-a-glucosamine. Because of its nontoxic, biocompatible, biodegradable and mucoadhesive properties, chitosan is widely used in the pharmaceutical field [171]. Chitosan has been used as a carrier system for hormones [172], proteins [173], enzymes [174], and genes [175]. Because of its apparent pKa = 5.6 [176], the application of chitosan in the oral administration of protein and peptide drugs is restricted by its easy dissolution in a low pH environment. 

General characteristics of chitosan produced in pilot plant... 

Recently, alkylchitosans were prepared giving interesting amphiphilic properties due to physical network formed by hydrophobic interaction between alkyl grafted chains they also have surface activity. [104-106] Grafting of N-isopropylaciylamide (NIPAm) or a ethylene oxide-propylene oxide copolymer (POEP) on chitosan produces thermosensitive polymers which may have new applications in controlled release. [107,108]An other thermosensitive systems was obtained when a glycerol-2-phosphate solution is added to a solution of chitosan up to pH around 7 the gel forms over 37°C. [109-111]... 

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