title: Direct production of itaconic acid from liquefied corn starch by genetically engineered Aspergillus terreus.
abstract: BACKGROUND
  Itaconic acid is on the DOE (Department of Energy) top 12 list of biotechnologically produced building block chemicals and is produced commercially by Aspergillus terreus. However, the production cost of itaconic acid is too high to be economically competitive with the petrochemical-based products. Itaconic acid is generally produced from raw corn starch, including three steps: enzymatic hydrolysis of corn starch into a glucose-rich syrup by α-amylase and glucoamylase, fermentation, and recovery of itaconic acid. The whole process is very time-consuming and energy-intensive.
  
  
  RESULTS
  In order to reduce the production cost, saccharification and fermentation were integrated into one step through overexpressing the glucoamylase gene in A. terreus under the control of the native PcitA promoter. The transformant XH61-5 produced higher itaconate titer from liquefied starch than WT. To further increase the titer by enhancing the secretion capacity of overexpressed glucoamylase, a stronger signal peptide was selected based on the major secreted protein ATEG_02176 (an acid phosphatase precursor) by A. terreus under the itaconate production conditions. Under the control of the stronger signal peptide, the transformant XH86-8 showed higher itaconate production level than XH61-5 from liquefied starch. The itaconate titer was further enhanced through a two-step process involving the vegetative and production phase, and the transformant XH86-8 produced comparable itaconate titer from liquefied starch to current one (~80 g/L) from saccharified starch hydrolysates in industry. The effects of the new signal peptide and the two-step process on itaconate production were investigated and discussed.
  
  
  CONCLUSIONS
  Itaconic acid could be efficiently produced from liquefied corn starch by overexpressing the glucoamylase gene in A. terreus, which will be helpful for constructing a highly efficient microbial cell factory for itaconate production and for further lowering the production cost of itaconic acid.
authors.forename: Xuenian
authors.initials: X
authors.lastname: Huang
authors.forename: Mei
authors.initials: M
authors.lastname: Chen
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Lu
authors.forename: Yueming
authors.initials: Y
authors.lastname: Li
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Laboratory of Biofuels, Shandong Provincial Key Laboratory of Energy Genetics, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No, 189 Songling Road, Qingdao 266101, China. lijj@qibebt.ac.cn.
authors.forename: Jian-Jun
authors.initials: JJ
authors.lastname: Li
mesh_terms: D001230:Aspergillus / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D018533:Biomass; D001709:Biotechnology / Q000379:methods*; D002950:Citrate (si)-Synthase / Q000235:genetics; D003001:Cloning, Molecular; D015180:Electrophoresis, Gel, Two-Dimensional; D005285:Fermentation; D005818:Genetic Engineering; D005087:Glucan 1,4-alpha-Glucosidase / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D021382:Protein Sorting Signals; D017384:Sequence Deletion; D013213:Starch / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism*; D013997:Time Factors; D014170:Transformation, Genetic
chemical_list: D021382:Protein Sorting Signals; D013386:Succinates; D013213:Starch; D002950:Citrate (si)-Synthase; D005087:Glucan 1,4-alpha-Glucosidase; D005947:Glucose; C005229:itaconic acid