title: Low molecular weight chitosans--preparation by depolymerization with Aspergillus niger pectinase, and characterization.
abstract: The viscosity of a chitosan solution was rapidly lowered in the presence of pectinase from Aspergillus niger at pH 3.0 and 37 degrees C. The low molecular weight chitosans (LMWC) had a molecular weight in the range 20,000-5000 Da. Circular dichroism spectra showed a decrease in the segment of acetylated glucosamine units, whereas X-ray diffraction and CP-MAS 13C NMR indicated higher crystallinity and polymorphism in LMWC. The latter on thermal drying resulted in structural alterations, and yielded an insoluble product. FT-IR and X-ray diffraction showed no evidence of either Schiff's base linkage or any annealed polymorph. CP-MAS 13C NMR showed marked changes in the chain conformations of LMWC, which are believed to be responsible for its loss of solubility and functionality.
authors.affiliation: Department of Biochemistry and Nutrition, Central Food Technological Research Institute, 570013, Mysore, India.
authors.forename: Farooqahamed S
authors.initials: FS
authors.lastname: Kittur
authors.forename: Acharya B
authors.initials: AB
authors.lastname: Vishu Kumar
authors.forename: Rudrapatnam N
authors.initials: RN
authors.lastname: Tharanathan
mesh_terms: D000107:Acetylation; D001234:Aspergillus niger / Q000201:enzymology*; D002240:Carbohydrate Sequence; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism; D048271:Chitosan; D002942:Circular Dichroism; D006026:Glycoside Hydrolases / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D008970:Molecular Weight; D011096:Polygalacturonase / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D014783:Viscosity; D014961:X-Ray Diffraction
chemical_list: D011108:Polymers; D002686:Chitin; D048271:Chitosan; D006026:Glycoside Hydrolases; C019868:chitosanase; D002688:Chitinases; D011096:Polygalacturonase