Preparation And Application Of Carboxymethyl β-Chitosan Oligomer With High Degree Of Deacetylation

β-chitosan with high degree of deacetylation was prepared by high temperature and concentrated alkali. It was shown that the best conditions were 45% NaOH, 95-100℃, 15h, and weight ratio of chitin/NaOH was 1/20.Many ways were used to decompose chitosan, such as with acid and with oxidant, and these methods often brought pollution. In this paper, cellulose enzyme was used to prepare chitosan oligomer. The optimal conditions were 50℃, pH5.0, 4h, and the concentration of cellulose enzyme to chitosan was 10%.The important actors of influencing yield and degree of substitution was dosage of NaOH, chloroactic acid, isopropyl alcohol, as well as temperature, reaction time and material proportion. The optimal material proportion was NaOH/chloroactic acid/isopropyl alcohol=5/5/1, and dosage of isopropyl alcohol could be chose according to the need of yield and degree of substitution. Reaction time and temperature respectively were 3h and 20-30℃. Prepared by above conditions, the degree of substitution was up 1.2.Results of GPC were Mn=1477.9, Mw=4040.5, Mw/Mn=2.73.And spectrum of IR and ¹³CNMR showed that carboxymethyl reaction has arisen inreaction process.Excellent antibacterial activity was showed when carboxymethyl 3 -chitosan oligomer was used in agriculture and food fields. It had good effect to restrain Pythinra. sp bacterium and B.cinerea bacterium of tomato, and high concentration solution had better effect than low concentration solution. The better antibacterial effect was showed too, when surface of ham was dipped with 2% solution and inside of ham was mixed with 0.2% solution.