Nitar Nwe

The Mechanical and Biological Properties of Chitosan Scaffolds for Tissue Regeneration Templates Are Significantly Enhanced by Chitosan from Gongronella butleri

Chitosan with a molecular weight (MW) of 104 Da and 13% degree of acetylation (DA) was extracted from the mycelia of the fungus Gongronella butleri USDB 0201 grown in solid substrate fermentation and used to prepare scaffolds by the freeze-drying method. The mechanical and biological properties of the fungal chitosan scaffolds were evaluated and compared with those of scaffolds prepared using chitosans obtained from shrimp and crab shells and squid bone plates (MW 105-106 Da and DA 10-20%). Under scanning electron microscopy, it was observed that all scaffolds had average pore sizes of approximately 60-90 μm in diameter. Elongated pores were observed in shrimp chitosan scaffolds and polygonal pores were found in crab, squid and fungal chitosan scaffolds. The physico-chemical properties of the chitosans had an effect on the formation of pores in the scaffolds, that consequently influenced the mechanical and biological properties of the scaffolds. Fungal chitosan scaffolds showed excellent mechanical, water absorption and lysozyme degradation properties, whereas shrimp chitosan scaffolds (MW 106Da and DA 12%) exhibited the lowest water absorption properties and lysozyme degradation rate. In the evaluation of biocompatibility of chitosan scaffolds, the ability of fibroblast NIH/3T3 cells to attach on all chitosan scaffolds was similar, but the proliferation of cells with polygonal morphology was faster on crab, squid and fungal chitosan scaffolds than on shrimp chitosan scaffolds. Therefore fungal chitosan scaffold, which has excellent mechanical and biological properties, is the most suitable scaffold to use as a template for tissue regeneration.

Production of fungal chitosan by solid state and submerged fermentation

The growth of the fungus Gongronella butleri USDB 0201 was compared in solid state fermentation (SSF) and submerged fermentation (SMF) using various nitrogen sources. The optimal production of biomass and chitosan by SMF was around 1.5–2.5 times higher than SSF. Urea is the best nitrogen source tested. SSF is to be preferred for the production of lower MW chitosan.

Effect of urea on fungal chitosan production in solid substrate fermentation

The fungus Gongronella butleri USDB 0201 was grown on sweet potato pieces supplied with different amounts of urea at 26 °C for 7 days under sterilized and humidified air supply. Crude chitosan was extracted from the fungal mycelia and treated with α-amylolytic enzyme to remove bound glucan. The distribution of the molecular weight of the chitosan was studied by gel exclusion chromatography. The conditions for optimal production of fungal chitosan by solid substrate (SS) fermentation have been investigated. The initial pH and the amount of urea influence the yield of fungal mycelia and chitosan. The importance of chitosan production by fungi is discussed.

Chitosan isolation from the chitosan-glucan complex of fungal cell wall using amylolytic enzymes

The chitosan/glucan complex isolated from the mycelia of the fungus, Gongronella butleri USDB 0201 can be cleaved with a heat-stable α-amylase at 65 °C for 3 h. This results in the removal of the glucan side chain and gives a chitosan solution with 100 times lower turbidity. It is proposed that chitosan and glucan chains are bound by an α(1 to 4) glucosidic bond. Both fungal chitosan and fungal glucan have been purified separately.

Production, Properties and Applications of Fungal Cell Wall Polysaccharides: Chitosan and Glucan

Chitosan and b-glucan have attracted increased interest for use in many pharmaceutical applications, especially in tissue engineering, medicine, and immu- nology. Commercially, chitosans are produced from the shells of shrimps and crabs and the bone plates of squids. In fungal cell walls, chitosan occurs in two forms, as free chitosan and covalently bounded to b-glucan. Low cost products of these two polymers could be produced using industrial waste mycelia and mycelia obtained from cultivation of fungus in medium obtained from industrial by-products. The quantity and quality of chitosan extracted from fungal mycelia depends on fungal strain, type of fermentation, fermentation medium composition such as trace metal content and concentration of nutrients, pH of fermentation medium, harvesting time of fungal mycelia, and chitosan extraction procedure. The growth of fungi in solid state/substrate and submerged fermentation, synthesis of chitosan and glucan in fungal cell walls, production of valuable products from fungi, production of chit- osan and glucan from fungal mycelia, and applications of chitosan and glucan are discussed in this chapter.

Isolation and characterization of chitin and chitosan from marine origin.

Nowadays, chitin and chitosan are produced from the shells of crabs and shrimps, and bone plate of squid in laboratory to industrial scale. Production of chitosan involved deproteinization, demineralization, and deacetylation. The characteristics of chitin and chitosan mainly depend on production processes and conditions. The characteristics of these biopolymers such as appearance of polymer, turbidity of polymer solution, degree of deacetylation, and molecular weight are of major importance on applications of these polymers. This chapter addresses the production processes and conditions to produce chitin, chitosan, and chito-oligosaccharide and methods for characterization of chitin, chitosan, and chito-oligosaccharide.