Study On Itaconic Acid Fermentation

Although the chemical synthesis routes to itaconic acid (IA, methylene succinic acid 97-65-4) production have also been examined, for example the dry distillation of citric acid, none of thses processes can really compete with fermentation by Asp.tereus and is practiced commercially. Therefore, it is very necessary to study deeply on the process of IA fermentation .This paper results are as follows:A strain,designated Asp.terreusTHA4lS producing LA with a high yield was successfully obtained by selecting at will and directive selection after Asp.terreus No.201 was treated by uv-irradiation, N-methy-N'-nitro-N-nitrosoguanidine(NTG), high temperature,diethyl sulphate(DES), uv- irradiation and LiCl simultaneously. Under the optimal conditions, Asp.terreusTHA418 could accumulate 93.8 g/L - 101.1 g/L LA from 140 g/L - 160 g/L glucose obtained by hydrolization of corn starch in shaking flask. The conversion ratio of sugar to IA and residual sugar in broth at the end of fermentation were 63.13%- 67.0% and 2.7 g/L-8.8 g/L respectively. This was the highest productivity ever reported. It is very efficacious in selection the high-pruducing IA strains by using 2-deoxy-D-glucose(DG) resistant agar plate and the high concentration IA agar plate containing with monofluoro acetic acid .To overcome the effect of glucose on IA synthesis ,increase the rate of fermentation and reduce the residual sugar in broth at the end of fermentation , mutagenic experiment was carried out by selection the DG resistant mutant using DG resistant agar plate. After the spores treated by mutagenic agent were cultivated in the synthetic medium of IA acting as only carbon source, the strains with high active IA oxidase could be eliminated through filter.The strains of mutants with high active aconitase and resistance to high IA concentration were selected by the help of high concentration LA agar plate containing with monofluoro acetic acid. The methods increased the chance of obtaining the strains of Asp.terreus with high producing IA.Characters of the Asp.terreus HAT418 were studied and compared with the parental strain Asp.terreus No.201. Asp.terreusHAT 418 could grow at 80g/L of IA agar plate, but the parental strain Asp.terreus No.201 couldn't. The sutiable conditions for Asp.terreusHAT418growth are 35-38 C, pH 4.5-6.0. It can utilize many carbon sources, but produce few spores in many cases. The suitable nitrogen sources are KNO3,NH4NO3 and (NH4)2SO4 .The effects of fermentation conditions on the production of IA by Asp.terreus HAT418 were studied in considerable detail. The results indicated that it could improve the production of IA when corn starch, glucose,sucrose or defatted corn powder et al acted as carbon sources, NH4NO3 as nitrogen source and corn steep liquor as auxiliary nitrogen source. The optimal start pH value and culture temperature are 3.0-3.5 and 36-38 C respectively. It was also found that the addition of MgSO4.7H2O could stimulate the growth of mycelia and IA production. CuSO4.5H2O could promote IA production. ZnSO4.7H2O could promote the sprout of spores of Asp.terreus HAT418 and IA production. Ca2+ could increase the proportion of IA to total acid in fermented liquor. The effects of other conditions such as incubation and dissolved oxygen on IA fermentation had been also studied. The optimal constitutes of medium and culture conditions determined were as follows:reducing sugar 140-160g/L MgSO4.7H2O 0.6-0.8 g/LNH4NO3 2-4 g/L CuSO4.5H2O 0.15 g/LZnSO4.7H2O 0.15 g/L CaCl2 0.1 g/LKH2PO4 0.25 g/L start pH 3.0-3.5fermentation temperature 36-38 CThe process of batch fermentation was investigated by culturing Asp.terreus HAT418 in 50L stirred tank reactor. The kinetics had been studied about batch fermentation of IA production by Asp.terreus HAT418. If the mycelia death and myceliolysis of Asp.terreus HAT418 were not con...