How Itaconic Acid Is Produced
Itaconic acid (CAS 97-65-4) is one of the most successful bio-based platform chemicals, and the reason is its production route: it is made by fermentation of sugars, not from petroleum. Understanding how the fermentation works — the organism, the feedstock, the recovery — explains both its sustainability credentials and its cost structure.
This article covers the historical thermal route, today’s industrial fermentation process, the recovery and purification steps, and the process-development trends that shape the market. For the full product background, see our main article on itaconic acid (CAS 97-65-4).
The Historical Route: Pyrolysis of Citric Acid
Itaconic acid was first made by the dry distillation of citric acid, which loses water and carbon dioxide on strong heating to give itaconic acid and related products. This route gave the material its early commercial availability, but it is inefficient, it consumes a more valuable feedstock, and it produces a mixture that requires careful purification. For these reasons it has been almost entirely displaced by fermentation, and it survives mainly as a historical footnote and as laboratory chemistry.
The Modern Route: Fermentation with Aspergillus terreus
Essentially all commercial itaconic acid is produced by aerobic fermentation of a carbohydrate feedstock using the filamentous fungus Aspergillus terreus. The organism secretes itaconic acid into the broth as a secondary metabolite, and the acid is then recovered and purified. The table below summarises the process stages.
| Stage | Purpose | Notes |
|---|---|---|
| 1. Medium preparation | Provide fermentable sugar and nutrients | Glucose, sucrose, starch hydrolysate or molasses; sterilised before use |
| 2. Inoculation | Introduce the production organism | Spores or a preculture of Aspergillus terreus |
| 3. Aerobic fermentation | Produce itaconic acid | Stirred, aerated bioreactor; controlled temperature, pH and dissolved oxygen; several days |
| 4. Biomass separation | Remove fungal biomass | Filtration or centrifugation |
| 5. Recovery | Isolate the acid from the broth | Crystallisation, or adsorption on ion-exchange resin followed by elution |
| 6. Purification and drying | Meet the specification | Concentration, crystallisation, drying to a white powder |
Why the Fermentation Is Demanding
Itaconic acid fermentation is well established, but it is not trivial to run economically. Several process variables have to be balanced:
- Oxygen supply. The fermentation is strongly aerobic, so aeration and agitation must be sufficient throughout the broth, which is viscous in filamentous cultures.
- pH control. The product is an acid, so the pH falls as it accumulates and must be controlled, typically by adding a base or by buffering, to keep the organism productive.
- Feedstock. Glucose and sucrose are the classic substrates; molasses and hydrolysates are attractive on cost but can introduce impurities and variability.
- Titre and yield. The economics depend heavily on how much itaconic acid the organism can produce per litre and per gram of sugar, which is why strain improvement is a core development activity.
- Downstream cost. Recovering a pure acid from a dilute broth is a significant part of the total cost, so recovery technology matters as much as fermentation.
Recovery and Purification
Two recovery strategies dominate. In the crystallisation route, the clarified broth is concentrated and cooled so that itaconic acid crystallises out and can be separated and dried. In the ion-exchange route, the acid is adsorbed onto a resin, washed, eluted and then concentrated and crystallised. Both routes aim to deliver a white crystalline product with controlled colour and a low level of related organic acids such as citraconic and mesaconic acid.
Process Development Trends
- Strain improvement. Classical mutagenesis and, more recently, metabolic engineering are used to raise titre and yield and to reduce by-products.
- Alternative feedstocks. Research targets cheaper and waste-derived sugars (for example lignocellulosic hydrolysates) to reduce feedstock cost.
- Alternative organisms. Yeasts and other hosts are being explored to simplify the process and improve robustness.
- Integrated recovery. More efficient separation technologies are being developed to lower downstream cost, which is the largest lever on the price of a fermentation-derived chemical.
What Buyers Should Take From This
Because the product comes from fermentation, its quality and price are tied to biological and downstream factors rather than to a petrochemical feedstock. For a buyer, the practical implications are:
- Consistency matters. Fermentation products can vary more between batches than petrochemical ones, so ask for batch history and a clear specification.
- Colour and related acids. These are the parameters that most often differ between suppliers.
- Bio-based story. If bio-based content is part of your product positioning, fermentation-derived itaconic acid supports that story natively.
- Documentation. Request the COA and any sustainability or regulatory statements you need.
Frequently Asked Questions
How is itaconic acid produced industrially?
By aerobic fermentation of sugars, using the mould Aspergillus terreus, followed by recovery, purification and drying.
Was itaconic acid ever made from citric acid?
Yes, historically by pyrolysis (dry distillation) of citric acid, but that route is inefficient and has been replaced by fermentation.
Why is itaconic acid considered bio-based?
Because its commercial production route is fermentation of renewable sugars rather than a petrochemical process.
What determines the cost of itaconic acid?
Mainly the cost of the sugar feedstock, the fermentation titre and yield, and the cost of recovery and purification.
Is fermentation-derived itaconic acid consistent in quality?
It can be, with good process control, but fermentation products tend to vary more between batches than petrochemical ones, so buyers should confirm the specification and review batch history.