Article

Mechanisms involved during the ultrasonically induced depolymerization of chitosan: characterization and control.

Universite de Lyon, Universite Lyon 1, UMR CNRS 5223 IMP, Laboratoire des Materiaux Polymeres et des Biomateriaux, Bat. ISTIL, 15, bd. A. Latarjet, F-69622 Villeurbanne Cedex, France.
Biomacromolecules (impact factor: 5.48). 04/2009; 10(5):1203-11. DOI:10.1021/bm8014472 pp.1203-11
Source: PubMed

ABSTRACT The existence of two mechanisms involved in the ultrasonically induced depolymerization of chitosan is evidenced. The first leads to a rapid scission of polymer chains and a lowering of the polydispersity, and the second is responsible for obtaining short polymer chains and oligomers with a polydispersity increase. A systematic experimental study allowed us to identify and quantify the main parameters influencing the chain scission kinetics. Consequently, using a "master curve" approach, a general law of variation of the molecular weight during the depolymerization is proposed. This law can be used in various experimental conditions to easily control the production of chitosan chains of precise length and low polydispersity or a collection of chito-oligosaccharides (COS). Characterization of the latter by (1)H NMR and MALDI-TOF mass spectrometry shows their high purity and an unchanged primary structure.

0 0
 · 
0 Bookmarks
 · 
33 Views
  • Source
    Article: Modification of genetic regulation of a heterologous chitosanase gene in Streptomyces lividans TK24 leads to chitosanase production in the absence of chitosan.
    Marie-Pierre Dubeau, Isabelle Guay, Ryszard Brzezinski
    [show abstract] [hide abstract]
    ABSTRACT: Chitosanases are enzymes hydrolysing chitosan, a β-1,4 linked D-glucosamine bio-polymer. Chitosan oligosaccharides have numerous emerging applications and chitosanases can be used for industrial enzymatic hydrolysis of chitosan. These extracellular enzymes, produced by many organisms including fungi and bacteria, are well studied at the biochemical and enzymatic level but very few works were dedicated to the regulation of their gene expression. This is the first study on the genetic regulation of a heterologous chitosanase gene (csnN106) in Streptomyces lividans. Two S. lividans strains were used for induction experiments: the wild type strain and its mutant (ΔcsnR), harbouring an in-frame deletion of the csnR gene, encoding a negative transcriptional regulator. Comparison of chitosanase levels in various media indicated that CsnR regulates negatively the expression of the heterologous chitosanase gene csnN106. Using the ΔcsnR host and a mutated csnN106 gene with a modified transcription operator, substantial levels of chitosanase could be produced in the absence of chitosan, using inexpensive medium components. Furthermore, chitosanase production was of higher quality as lower levels of extracellular protease and protein contaminants were observed. This new chitosanase production system is of interest for biotechnology as only common media components are used and enzyme of high degree of purity is obtained directly in the culture supernatant.
    Microbial Cell Factories 02/2011; 10:7. · 3.55 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

chain scission kinetics
 
chitosan chains
 
COS
 
depolymerization
 
general law
 
main parameters influencing
 
MALDI-TOF mass spectrometry
 
master curve
 
polydispersity increase
 
polymer chains
 
precise length
 
short polymer chains
 
ultrasonically induced depolymerization
 
unchanged primary structure
 
various experimental conditions