Methods for producing modified microcrystalline chitosan and uses therefor

Abstract

Disclosed are methods of producing modified microcrystalline chitosan. Chitosan in aqueous solution is degraded enzymatically, hydrolytically or oxidatively. The chitosan solution is then alkalized with agitation using aqueous hydroxides and/or their salts to attain a pH not lower than 7.0. The precipitated modified microcrystalline chitosan is highly pure and may be concentrated and dried according to known methods. Methods according to the invention also include methods by which an aqueous solution of chitosan is first alkalized using hydroxides and/or their salts to a pH not lower than 7.0. Then the precipitated microcrystalline chitosan is subjected to enzymatic or oxidative degradation to achieve a desired average molecular weight and polydispersity. The product is highly pure and may be concentrated and dried according to known methods.

1 - 33 . (canceled)  
   
   
       34 . A method to produce a chitosan-calcium complex from a microcrystalline chitosan, comprising the steps of: 
 (a) providing a suspension containing ≧0.01 wt % microcrystalline chitosan, said chitosan having an average polymerization degree ≧100 kD, a polydispersity ≧2.0, and deacetylation degree ≧65%; and    b) mixing said microcrystalline chitosan with ≧0.01 wt % calcium (II) salt to form said complex; wherein said complex has a water retention value ≧300% and a pH 27.0.    
   
   
       35 . A method according to  claim 34 , wherein said calcium (II) salt is selected from the group consisting of calcium chloride and calcium acetate.  
   
   
       36 . A method according to  claim 34 , wherein said calcium (II) salt concentration is 10-50 wt % relative to chitosan.  
   
   
       37 . A method according to  claim 34 , wherein said mixing step is carried out at a temperature .gtoreq.10.degree. C.  
   
   
       38 . A method according to  claim 38 , wherein said mixing step is carried out at a temperature between 20.degree. C. and 40.degree. C.  
   
   
       39 . (canceled)