Itaconic Acid Fermentation Using Potato Starch

Itaconic acid is the important industrial raw material and additives inchemical fields. The widespread use of itaconic acid in production of syntheticresin, plastic and pharmaceutics surfactant has resulted in an increased demandfor itaconic acid product. With the rapid development of world economy, twomajor problems loom large in the shortage of energy and environmentalpollution. The appearance of biorefinery provides a new approach forsustainable environment development and green energy exploitation. As a bigproducer of potato, our country ranks first in the world in both acreage andproduction. So, potato industry has a huge developing space and brightdeveloping prospects in Chinese. The industrialization of itaconic acidfermentation by potato starch to achieve, not only increases income of peasants,promotes the countryside industrial structure adjustment, but also protectsenvironment and promotes energy efficiency and conservation.In this work, the research of itaconic acid fermentation which using potatostarch was performed. With Aspergillus terreus CICC40205as a starting strain,mutation breeding was carried out to obtain mutated strains with higher itaconicacid yield. The medium composition and fermentation process were optimizedto further enhance the itaconic acid productivity. The main research contentsand results were as follows:Aspergillus terreus CICC40205as a starting strain was stepwise mutatedwith ultraviolet light and Diethyl sulfate. One itaconic acid high-producingstrain AT-DES-63was screened through plate culture screening, shake flaskscreening and continuous passage cultivation. This strain could produce itaconicacid5.32g/L after fermentation under the fermentation condition without beingoptimized.The seed medium was optimized by orthogonal design experiment and theseed age was also studied. The optimum values were carbon resourceconcentration40g/L, NH₄NO₃4g/L, Corn steep liquor （CSL）2g/L, MgSO₄·7H₂O2g/L, pH4.0and the optimal seed age was42h.According to the single factor experiment of shaking-flask fermentation,statistically-based experimental designs were employed to optimize the itaconicacid fermentation using potato starch. Firstly, pH, rotational speed andfermentation temperature were chosen as the major factors by Plackett-Burmandesign. Meanwhile, the central composite experimental design and responsesurface analysis were used to optimize the levels of major factors. A secondorder quadratic equation was established, and the applicability of the model andinteraction involved factors on predicting the itaconic acid yield was verified.The itaconic acid yield reached6.08%under optimized conditions, which was14.3%higher than that under the original conditions.By the preliminary study of shaking-flask fermentation, the suitable initialcarbon source concentration was ranged from110g/L to130g/L and the optimalnitrogen source was CSL and NH₄NO₃. Plackett-Burman design was used in thefirst step to evaluate the effects of9variables on the itaconic acid yield. Initialcarbon resource concentration, CSL, MgSO₄·7H₂O and KH₂PO₄were screenedas significant factors and their levels were further optimized using the methodsof response surface analysis. The optimum values were initial carbon resourceconcentration130g/L, CSL2.14g/L, MgSO₄·7H₂O2.19g/L, KH₂PO₄0.14g/L,NH₄NO₃3g/L, FeSO₄·7H₂O0.10g/L. A maximum itaconic acid yield of7.04%was obtained under optimizing conditions.Fed batch fermentation was studied with Aspergillus terreus AT-DES-63according to the optimal conditions of batch fermentation. The optimum initialglucose concentration and nitrogen concentration were50g/L and1g/L,respectively. The intermittent feeding was performed at the48h,60h,72h,84h,respectively. The itaconic acid yield reached8.39%under fed batchfermentation, which was19.2%higher than that under the batch fermentation.The high performance liquid chromatography （HPLC） was built to detectitaconic acid in fermentation broth, which was quick and efficient.Itaconic acid was isolated and purified from fermentation broth byconcentrated crystallization process and the crystallographic texture waselucidated by X-ray diffraction method.