Kudrat Pirniyazov

In the present work, chitosan nanoascorbate Bombyx mori (CSNA) based on high-molecular-weight chitosan (CS) and ascorbic acid (AA) was synthesized by ionotropic

Oligochitosan samples were obtained by acid hydrolysis of high molecular weight chitosan isolated from Bombyx mori (B.M.). Carrying out acid hydrolysis for 6 hours, it was found that after 4 hours and further with increasing duration, the molecular weight of chitosan decreases to a value corresponding to the ranges of mo-lecular weights of oligochitosan 2–16 kDa. It has been seen that the optimal duration of hydrolysis, leading to the production of oligochitosan with a molecular weight of less than 16 kDa, should be considered 4–5 hours. Depolymerization of chitosan with a molecular weight of 177 kDa was carried out using sodium nitrite in so-lution to obtain oligochitosan with a molecular weight of 6 kDa. On the basis of oligochitosan samples ob-tained by two methods, their ascorbates were received. Under constant conditions with varying the ratio of the components (ChS:AA) and the pH of the solution, the reaction of chitosan ascorbate formation was car-ried out on the basis of the suspension method. The composition, structure, and molecular weight characteris-tics of oligochitosan ascorbate and oligochitosan Bombyx morisamples were confirmed by physicochemical methods. It has been seen that the obtained samples have antimicrobial properties against Fuzarium oxysporum.

In this work, for the first time, a water-soluble natural biopolymer of chitosan ascorbate based on Bombyx moni chitosan and ascorbic acid was obtained and kinetic features of the process were determined. Samples of chitosan ascorbate were synthesized, the interaction of chitosan with ascorbic acid was studied by analytical titration. The synthesis was carried out in order to determine the activation energy of formation of the reaction of chitosan ascorbate, in the ratio of chitosan and ascorbic acid (4:1) components for 15 minutes with a reaction temperature ranging from 25 degrees C to 65 degrees C. The results of the kinetic studies show that in the interaction under the study the reaction order on ascorbic acid concentration exceeds the reaction order on chitosan concentration, while the reaction activation energy was determined, which equals to 13.38 kJ/mol. This result allows us to conclude that during the formation of chitosan ascorbate at 55 degrees C the highest equilibrium constant is established, and a further increase in temperature leads to a decrease in the yield and equilibrium constant. The results obtained indicate that with an increase in the concentration of ascorbic acid compared to the one of chitosan, the reaction rate increased almost twice. It was found that with an increase in the reaction time, the average rate of synthesis gradually decreases. This is due to the fact that with an increase in the duration of the reaction in the solution the concentration of unbound (free) ascorbic acid decreases, and as a result, the reaction rate decreases as well.