Selection Of Alcohols As Complexing Agent For The Enzymatic Preparation Of α-cylcodextrin And Its Mechanism Analysis

It is well known that the proportion and yield of α-, β-and γ-cyclodextrin can be changedby the addition of certain organic solvents as complexing agent during the enzymaticpreparation of cyclodextrin. In this paper, an efficient seperation method was developed.Another purpose of this paper was to illustrate the influence law and mechanism of the yieldand selectivity of α-cyclodextrin by adding a serie of alcohols, and then provide thetheoretical basis for the choice of complexing agent in the enzymatic preparation ofα-cyclodextrin. The main contents are as follows:1. An extraction method was developed to separate the complex reagent alcohols inenzymatic reaction system for α-cyclodextrin production. Effect of type and volume ofextraction solvent, extraction time, and extraction temperature on extraction separation of1-decanol which was chosen as the main obeject of study were investigated. The resultsshowed that the optimum conditions were that ethyl ether,15times as many as the volume of1-decanol, was used as extraction solvent to extract1-decanol at30℃for30min. Secondly,under above optimum conditions,1-decanol in enzymatic reaction system for α-cyclodextrinproduction was extracted. The results showed that, after extraction separation of1-decanol,the yields of α, β and γ-cyclodextrin determined were almost the same as those by thetraditional separation method—steam distillation, which further verified that1-decanol in theα-cyclodextrin-1-decanol complexes could be effectively separated using extraction method.Furthermore, compared with steam distillation, the proposed extraction method was simple,energy-saving and efficient.2. The effects of monobasic straight-chain alcohols, branched-chain alcohols and diolson the enzymatic preparation of α-cyclodextrin were studied, respectively. The resultsindicated that the yied of α-cyclodextrin was more significantly shifted by straight-chain andthe bigger molar structure of alcohols, the more unfavorable to the preparation ofα-cyclodextrin.The law of the effect of monobasic straight-chain alchols counted as fllows:(1)the alcohols with carbon atom number below3had no significant effect, the highest yield ofα-cyclodextrin compared with the reaction system was only promoted by52.67%~173.45%.(2)The alcohols with carbon atoms between3and8were in favor of the preparation ofα-cyclodextrin. The yield were obtained4~5fold.(3) The alcohols with8above carbon atomswere the best for α-cyclodextrin, The yield were obtained5~6fold. The yield andproportation of α-cyclodextrin were4.67%and30.60%without any compound,while theyields of α-cylcodextrin were28.60%、33.41%and29.33%in the presence of32mmol/Loctanol, decanol and dodecanol, respectively.3. The mixture of ethanol and decanol as the compound in the preparation of α-cyclodextrin was carried out. The result showed that44.35%yield was obtained in thepresence of1.5%(v/v) decanol and2%(v/v) ethanol,which was almost equal to the additon of6%(v/v) decanol which used in α-cyclodextrin industrial production. It is obviously that theethanol/decanol mixture reduced the use of toxicity and high-price decanol,lower the cost ofpreparation of α-cyclodextrin and had a good application prospect.4. The competitive UV-Vis spectrophotometric method was performed to determin thecomplex stability constants and thermodynamic parameters for α-cyclodextrin and alcoholswith methyl orange as spectrol probe. It was found that The selection of compound wasdetermined by the inclusion ability between compound and cyclodextrin. The more stable theinclusion complex, the more obvious of the promoting effect of the preparation ofα-cyclodextrin. The most important factors of the inclusion complex were the size matchingbetween cyclodextrin and alcohols, the hydrophobic, hydrogen bonding and molecularpolarity, and so on.