Abstract:

The optimal conditions for the synthesis of chitosan oligosaccharide-hydrolyzed gliadin copolymer by roughly-purified microbial transglutaminase(MTGase) catalysis were investigated, and the structures of obtained copolymer were characterized. These optimal conditions are estimated as the substrates mass ratio of chitosan chitosan oligosaccharide and hydrolyzed gliadin is 1:40 under pH 6.00~6.50, and 50 min stirring at 50 ℃. The grafting rate at these conditions can reach up to 60%~70%. Infrared spectrum analysis of the copolymer shows that, compared with chitosan oligosaccharide, the introduction of electron withdrawing group to chitosan oligosaccharide-hydrolyzed gliadin copolymer has inductive effects on the amide C=O, and causes the vibration peak shift to higher wave number with enhanced absorption intensity. DTA curve indicates that the chitosan oligosaccharide-hydrolyzed gliadin copolymer begins to lose the associated water at 60.91 ℃, melt at 387.55 ℃, and completely degrade at 665.25 ℃. This is significantly different to that of chitosan oligosaccharide and gliadin. XRD analysis shows that the crystallinity of grafted copolymers is greatly reduced, the cell data is different from those of chitosan oligosaccharide. HPLC analysis shows that the copolymer has two main components, accounting together for 80.6% of the total mass. The relative molecular masses of the two main components are 66069 and 27285, respectively. The copolymer does not dissolve in water and many organic solvents, but is slightly soluble in 1% NaOH, with a solubility at 0.184 mg/100 g. The melting range of the copolymer is 162~163 ℃.

Key words: microbial transglutaminase, chitosan oligosaccharide, hydrolyzed gliadin, copolymer