The Study On Biological Preparation Of Gallic Acid By Immobilized Aspergillus Niger

In this study,Aspergillus niger B1401 was used as tannase-producing strain,Aspergillus niger was immobilizated to biologically produce gallic acid with tannin.Using the content and yield of gallic acid as reference indexes,the different method and carriers of immobilized Aspergillus niger,the preparation of immobilized Aspergillus niger and the gallic acid with tannin by immobilized Aspergillus niger were studied.In the end,we obtained the following conclusions:The gallic acid production of immobilized Aspergillus niger was studied using different immobilized carriers with different immobilized methods,such as adsorption,embedding and crosslinking.The most suitable method of immobilization was adsorption and the best immobilized carrier was reticular polyester fiber,then the yield of gallic acid reached 53.79%and also the separation of products was easier.The process conditions about gallic acid preparation of immobilized Aspergillus niger was studied.The optimization results of single factor were exactly consistent with the optimization results of response surface,the optimum conditions were:the load of the carrier was 1.5 g,the size of the carrier was 1 cm³,the inoculation amount was 2.5%(v/v),the fermentation time was 132 h,the p H of initial reaction solution was 5.0,the temperature of enzyme cultivation was 35?,the speed of enzyme cultivation was 180 r·min^-1,the industrial tannic acid was added to the amount of 204mg·m L^-1by batchs,the stirring speed of transformation was 140 r·min^-1.Under these conditions,the yield of gallic acid could reach 76.07%,it was increased 22.28%that compared with unoptimizing which the yield of gallic acid was 53.79%.The optimal temperature of transformation was 35?and optimal p H was 4.0,comparing with free cells,the optimal temperature increased 5?and the optimum p H decreased 0.5 units of p H.The stability of immobilized Aspergillus niger was better than the fermentation of free cell.The temperature and p H stability range was20?-60?and 4.0-6.0.Compared with the free cell,the stability range of temperature and p H was increased 10?and 1.0 unit respectively.The p H adjustment method of immobilized Aspergillus niger was compared during transformation process.It was found that the ammonia to adjust p H was better in transformation process.The repeating transformation processing of immobilized Aspergillus niger found that it was more reasonable that deal with the immobilized cells using the way of separation but no-washing and add ammonia.The yield rates were about 59.52%after 24 batchs of conversion,which the time of repeat transformation was got 1236h.When the immobilized cells were excessived,the immobilized cells were divided into two parts to continuous to repeat transformation,the results showed that the approach was available.At the same time,adding a certain amount of reticular polyester fiber during the separation transformation processing is perfectly.The adding concentration of industrial tannins during the immobilized cells were repeated transformation was optimized.As a results the best adding concentration was 180 mg·m L^-1.The amplification of 5 L fermenter was preliminary explored,shows that the result is better than shaking transformation.Immobilized Aspergillus niger was repeated transformation 6 batchs in the 5 L fermentor,the yield of gallic acid was stablility about 71.39%.Compared with the yield of gallic acid in shaking transformation which was 62.78%,the average rates have been increased 8.61%.The gallic acid production of immobilized Aspergillus niger is feasible and has good industrial potential value have been proved.