Direct production of itaconic acid from liquefied corn starch by genetically engineered Aspergillus terreus

Abstract

BackgroundItaconic 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.ResultsIn 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.ConclusionsItaconic 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-014-0108-1) contains supplementary material, which is available to authorized users.

Emerging biotechnologies for production of itaconic acid and its applications as a platform chemical

“…This value was 70% of that produced from glucose (120 mg mL −1 ). Huang et al [32] reported that IA could be efficiently produced from liquefied starch by overexpressing the glucoamylase gene from A. niger under the control of the native citrate synthase promoters (PcitA3 and PcitA4) in A. terreus. The overexpressed glucoamylase could be effectively secreted out of cells by its native signal peptide.…”

Itaconic acid production from glycerol using Escherichia coli harboring a random synonymous codon‐substituted 5′‐coding region variant of the cadA gene

“…In addition, valuable chemicals derived from fossil fuels, such as acrylic acid, acetone cyanohydrin, maleic anhydride, and sodium tripolyphosphate, could be replaced by IA (Pomogailo et al, 2010;Shang et al, 2009). Although IA has the potential for market extension, relatively high production costs restrict its availability (Huang et al, 2014a). Until now, various studies, including those employing optimization of culture conditions and the improvement and development of hosts, have tried to improve production yield.…”

Establishing an efficient gene-targeting system in an itaconic-acid producing Aspergillus terreus strain

“…Hence, a multitude of candidate transformants have usually to be analyzed in order to identify the correct one, which makes fungal transformation laborious, tedious and time-consuming. The expression cassette of target gene is randomly integrated into the genome which is not ideal for the comparison of phenotypes between different mutants (Huang et al 2014a). However, exogenous NDA can be mainly integrated into the genome through HR in the NHEJ-pathway defective mutant (Ishibashi et al 2006).…”