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Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues.

ABSTRACT: Several fungi and starch-rich industrial residues were screened for itaconic acid (IA) production. Out of 15 strains, only three fungal strains were found to produce IA, which was confirmed by HPLC and GC-MS analysis. These strains were identified as Aspergillus terreus strains C1 and C2, and Ustilago maydis strain C3 by sequencing of 18S rRNA gene and internal transcribed spacer regions. Cis-aconitate decarboxylase (cad) gene, which encodes a key enzyme in IA production in A. terreus, was characterized from strains C1 and C2. C1 and C2 cad gene sequences showed about 96% similarity to the only available GenBank sequence of A. terreus cad gene. 3-D structure and cis-aconitic acid binding pocket of Cad enzyme were predicted by structural modeling. Rice, corn and potato starch wastes were screened for IA production. These materials were enzymatically hydrolyzed under experimentally optimized conditions resulting in the highest glucose production of 230 mg/mL from 20% potato waste. On comparing the production potential of selected strains with different wastes, the best IA production was achieved with strain C1 (255.7 mg/L) using potato waste. Elemental composition as well as batch-to-batch variation in waste substrates were analyzed. The difference in IA production from two different batches of potato waste was found to inversely correlate with their phosphorus content, which indicated that A. terreus produced IA under phosphate limiting condition. The potato waste hydrolysate was deionized to remove inhibitory ions like phosphate, resulting in improved IA production of 4.1 g/L by C1 strain, which is commercially competitive.

SUBMITTER: Bafana R

PROVIDER: S-EPMC5574779 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues.

Bafana Richa R Sivanesan Sarvanadevi S Pandey R A RA

Indian journal of microbiology 20170710 3

Several fungi and starch-rich industrial residues were screened for itaconic acid (IA) production. Out of 15 strains, only three fungal strains were found to produce IA, which was confirmed by HPLC and GC-MS analysis. These strains were identified as Aspergillus terreus strains C1 and C2, and Ustilago maydis strain C3 by sequencing of 18S rRNA gene and internal transcribed spacer regions. Cis-aconitate decarboxylase (cad) gene, which encodes a key enzyme in IA product ...[more]

PMID: 28904417

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Project description:BackgroundItaconic acid is a promising platform chemical for a bio-based polymer industry. Today, itaconic acid is biotechnologically produced with Aspergillus terreus at industrial scale from sugars. The production of fuels but also of chemicals from food substrates is a dilemma since future processes should rely on carbon sources which do not compete for food or feed. Therefore, the production of chemicals from alternative substrates such as acetate is desirable to develop novel value chains in the bioeconomy.ResultsIn this study, Corynebacterium glutamicum ATCC 13032 was engineered to efficiently produce itaconic acid from the non-food substrate acetate. Therefore, we rewired the central carbon and nitrogen metabolism by inactivating the transcriptional regulator RamB, reducing the activity of isocitrate dehydrogenase, deletion of the gdh gene encoding glutamate dehydrogenase and overexpression of cis-aconitate decarboxylase (CAD) from A. terreus optimized for expression in C. glutamicum. The final strain C. glutamicum ΔramB Δgdh IDHR453C (pEKEx2-malEcadopt) produced 3.43 ± 0.59 g itaconic acid L-1 with a product yield of 81 ± 9 mmol mol-1 during small-scale cultivations in nitrogen-limited minimal medium containing acetate as sole carbon and energy source. Lowering the cultivation temperature from 30 °C to 25 °C improved CAD activity and further increased the titer and product yield to 5.01 ± 0.67 g L-1 and 116 ± 15 mmol mol-1, respectively. The latter corresponds to 35% of the theoretical maximum and so far represents the highest product yield for acetate-based itaconic acid production. Further, the optimized strain C. glutamicum ΔramB Δgdh IDHR453C (pEKEx2-malEcadopt), produced 3.38 ± 0.28 g itaconic acid L-1 at 25 °C from an acetate-containing aqueous side-stream of fast pyrolysis.ConclusionAs shown in this study, acetate represents a suitable non-food carbon source for itaconic acid production with C. glutamicum. Tailoring the central carbon and nitrogen metabolism enabled the efficient production of itaconic acid from acetate and therefore this study offers useful design principles to genetically engineer C. glutamicum for other products from acetate.

Dataset Information

Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues.

Publications

Itaconic Acid Production by Filamentous Fungi in Starch-Rich Industrial Residues.

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