Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Characterization of a New Antifungal Chitin-Binding Peptide from Sugar Beet Leaves

Abstract: The intercellular washing fluid (IWF) from leaves of sugar beet (Beta vulgaris L.) contains a number of proteins exhibiting in vitro antifungal activity against the devastating leaf pathogen Cercospora beticola (Sacc.). Among these, a potent antifungal peptide, designated IWF4, was identified. The 30-amino-acid residue sequence of IWF4 is rich in cysteines (6) and glycines (7) and has a highly basic isoelectric point. IWF4 shows homology to the chitin-binding (hevein) domain of chitin-binding proteins, e.g. class I and IV chitinases. Accordingly, IWF4 has a strong affinity to chitin. Notably, it binds chitin more strongly than the chitin-binding chitinases. A full-length IWF4 cDNA clone was obtained that codes for a preproprotein of 76 amino acids containing an N-terminal putative signal peptide of 21 residues, followed by the mature IWF4 peptide of 30 residues, and an acidic C-terminal extension of 25 residues. IWF4 mRNA is expressed in the aerial parts of the plant only, with a constitutive expression in young and mature leaves and in young flowers. No induced expression of IWF4 protein or mRNA was detected during infection with C. beticola or after treatment with 2,6-dichloroisonicotinic acid, a well-known inducer of resistance in plants.

Current trends in fungal biosynthesis of chitin and chitosan

Abstract: Chitin and chitosan are natural biopolymers found in shell of crustaceans, exoskeletons of insects and mollusks, as well as in the cell walls of fungi. These biopolymers have versatile applications in various fields such as biomedical, food industry, and agriculture. These applications are back to their biocompatibility, biodegradability, strong antibacterial effect, and non-toxicity. The fungal biopolymers have many features that made them more advantageous than those biopolymers from seafood waste origin. Chitin and chitosan are not components of cell wall in all fungal species. The fungal classes of Basidiomycetes, Ascomycetes, Zygomycetes, and Deuteromycetes are known to contain chitin and chitosan in their cell walls. The amounts and characters of fungal biopolymers are affected by many factors so they should be optimized before increasing the scale of production. The statistical design of experiments is the most recent and advanced approach for optimization of various factors with more reliable results. Although extensively studied, further studies concerning fungal chitin and chitosan should be conducted in order to be sure of safety for human use.

Purification of a thermostable endochitinase from Streptomyces RC1071 isolated from a cerrado soil and its antagonism against phytopathogenic fungi.

Abstract: Aims: The chitinolytic activity of an actinomycete, isolated from a tropical acidic ferrasol (FAO) under cerrado (savanna) vegetation, is reported. Methods and Results: Selection of the strain was based on spot inoculation on solid colloidal chitin medium. The use of chemotaxonomic, morphological and physiological procedures placed it in the Streptomyces genus, but identification to species level could not be achieved. A protein with endochitinase activity was isolated and purified from the supernatant fluid by concentration, precipitation, hydrophobic interaction, gel filtration and adsorption procedures. The molecular size of the purified chitinase was estimated by gel filtration to be 70 kDa, and its pI was 6·1. The enzyme had temperature and pH optima of 40°C and 8·0, respectively, and showed thermal (30–70°C) and pH (4–9) stabilities. Antifungal activity of the selected strain was observed following in vitro experiments using growing cells, crude extract or the purified endochitinase, and by detecting growth inhibition of the tested phytopathogenic fungi. Conclusions: Strain Streptomyces RC 1071 could not be placed into any known species, suggesting a new taxon. The purified endochitinase presented similar molecular weight, optimum temperature and pH activity, and stability of other endochitinolytic enzymes reported in the literature. In all three in vitro experiments performed, inhibition of growth of the phytopathogenic fungi used as test organisms was observed. Significance and Impact of the Study: Some of the endochitinase characteristics such as thermal stability, as well as pH tolerance, are very interesting for biotechnological purposes. In addition, due to its antifungal activity, Streptomyces RC 1071 seems promising for use in biological control.