Research On The Effect Of Starch Pretreatment On Preparation Of Cyclodextrin

Cyclodextrin is a kind of macrocyclic compound ,which can be widely used in medicine, food, agriculture and cosmetics. Cyclodextrins are produced from starch catalyzed by cyclodextrin- glucanotransferase (CGTase). The production process can be divided into solvent and solvent-free method. Solvent method can get a high cyclodextrin yield. But the solvent limits the application with a high cost and it is harmful to human health and environment. Solvent-free method is a new way to ptoduct cyclodextrins has not complexing agent in it's process with no harm. In food, medicine and cosmetics area, the solvent-free method has a great demand. But high-cost extraction process makes the solvwnt-free method difficult to be adopted in industrial manufacturing. Experements were done to get a simple solvent-free process with a high conversion rate, especiallyβ-cyclodextrin.Research were done to get the factors affecting the catalysis of starch by cyclodextrin glucanotransferase (CGTase), the results showed that, pH8.5, 65℃is the optimized reaction condition, while the enzyme activity is reduced rapidly. In the producing process, the enzyme activity loss can be relieved by changing the method of adding enzyme; A highβ-cyclodextrin conversion rate was gotten by adding 5U/g starch, excessive enzyme can cause hydrolysis and reduce the yieldof cyclodextrin. Ca2+ is a protecting agent of the enzyme, but EDTA, MgSO4, KCl, FeCl3 have inhibition effects on enzyme, so they have to be avoided in the producing process.Effects of different pretreatment of starch on cyclodextrin production were investigated. Screening, ultrasonic, microwave, pasting and hydrolysis using corn starch as substrate has been done to improve the conversion rate of cyclodextrin production. Effects of the size of starch granules, the damage extent of crystalline structure and the inhabition of micromolecular sugar on the cyclodextrin production was investigated and it was proved that CGTase preferred gelatinized starch(but its high viscosity interfere its use in industrial manufacture.).On the basis of the process parameters ofβ-cyclodextrin using starch as substrate and effects of different pretreatment of starch on cyclodextrin production, a moderate heated method was proposed, corn starch was heated at 85℃450r/min for 1h, 1.25U/g starch CGTase was added at 0,2,4and6h , after 8h's reaction, total cyclodextrin conversion rate was 37.63% and the concentration was 48.65mg/mL,β-cyclodextrin conversion rate was 24.68% and the concentration was 31.69mg/mL, higher than the traditional method which obtained cyclodextrin conversion (24.87%)and concentrate(37.30mg/mL),with theβ-cyclodextrin conversion rate (14.80%) and concentration(22.20mg/mL) after reacting for 12h. The advantages of this method were a high conversion rate, low cost, easy to operate, which may significantiy impact industrial manufacture.