Studies On The Application Of Making Astaxanthin From Natural Lutein By Modification

The thesis mainly relates to a process for preparing astaxanthin from lutein eaters. The process includes hydrolyzation of lutein esters, isomerization of lutein to zeaxanthin, and bromization and oxidation of zeaxanthin.The paper provides a process for hydrolysis, separation and purification lutein from lutein ester. Lutein ester was homogenized with alcohol, under sealed condition at 56℃, then the mixture was subjected to hydrolyzation with the solution of aqueous alkali for 3 h, with hydrolyzation yields near to 100%. The hydrolyzed product was mixed with warm water and centrifuged and evaporated under vacuum to remove solvent phase. The purity of lutein was up to 70% with UV and HPLC. 60% of the original lutein content was recovered.The reaction kinetics for the hydrolysis of lutein esters was investigated. The reaction was regarded as a first order reaction when alkali was much more than needed. When 100 g lutein esters were homogenized with 90 ml alcohol, the mixture was subjected to hydrolyzation with 20 g alkali. The expression of the concentration of lutein and the reaction time is as follows:C_lutein=0.435 [ 1-exp(-0.02305t) ] Where C_lutein is the concentration of lutein in the solution at reaction time.The paper provided a process for isomerization of lutein to zeaxanthin. It can yield high purity zeaxanthin by separation and purificantion. Lutein was mixed with alcohol and alkali, under sealed condition and inert atmosphere reacted for 24 h at about 110℃, with isomerization yields near to 70% by HPLC. The isomerized product was dissolved in chloroform, washed with water for several times. The solvent was recovered from the liquid fraction by evaporation leaving an oily residue. Under these conditions, the final substrate has a zeaxanthin content of about 50%, comparing to the initial content of 3%.The paper provided a process for bromization and oxidation of high purity zeaxanthin to astaxanthin. High purity zeaxanthin was mixed with a solution of aqueous sodium chlorate under ice water. The solution was added to the stirred zeaxanthin solution over a period of 4 to 6 hours under nitrogen. Upon completion of the reaction, the organic layer was washed with water. The final substrate was identified and qualitied with HPLC and MS, which indicated good formation of the desired astaxanthin product. The concentration of astaxanthin was up to 10%.Postgraduate student: Xuli Dong (Applied Chemistry)Directed by Prof. Lixin Zhang Hui Zhang...