Genetically Re-engineered Microorganisms to Convert Waste Into High-Value Chemicals

Researchers have genetically reengineered a microbe to transform waste into itaconic acid, a precious, high-value chemical used in paints and plastics.

In the study, "Production of itaconic acid from alkali pretreated lignin by dynamic two stage bioconversion" published in Nature Communications, scientists at Oak Ridge National Laboratory effectively bioengineered the bacteria for itaconic acid production, thus making dynamic controls, separating growth and production stages of the microbes to enhance efficiency and acid yield.

What is Itaconic Acid?

Itaconic acid or methylene succinic acid is a high-value chemical that is used in the polymer industry, wastewater treatment, and ion-exchange chromatography. Such can be turned to the chemical 3-methyltetrahydrofuran, which has greater emission and combustion capabilities than gasoline. Industrial production of itaconic acid is done with fungus Aspergillus terreus using glucose as its solitary carbon source.

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Itaconic acid production would also include fungi, which feed on pure sugar, which can be costly. Researchers utilized lignin, which is waste from paper mills and biorefineries, to develop the microbe Pseudomonas putida and accomplish a possibly inexpensive itaconic production.

Utilizing Dynamic Controls to Realize Itaconic Acid Production

The researchers' secret was to utilize dynamic controls to delineate the bacterial growth stage from itaconic acid production, a Phys.Org article said. A biosensor was designed and deployed at the ORNL to activate the metabolic pathway of itaconic acid production. This consumes the nitrogen that harnesses their growth.

In addition to lignin, the researchers also showed the potential for Pseudomonas putida to vaporize other biomass streams. This includes thermochemical wastewater and lignocellulosic sugar hydrolysates. The study likewise demonstrated itaconic acid from various substrates that may be found in possible commercial feedstocks, such as biodiesel waste or glycerol, lipids that include octanoic acid, and plant biomass, such as aromatics, acetic acid, and sugars. Thus, the technology could provide a universal platform for a two-phase production of a wide array of chemicals from several alternate sources beyond lignin.

Bringing Added Revenue to Biorefineries

Such technology, the researchers said, could bring added revenue to the biorefinery by converting lignin into precious, high-value chemicals. A strain, they added, reached about 90 percent of the theoretical yield at the production stage and was further optimized. Such techniques could also be used in other carbon waste streams.

Previous studies showed, that itaconic acid production was achieved through several other bioengineering processes, a Science Direct article said.

In one study, itaconic acid was produced through a metabolically engineered Neurospora crassa fungus using the lignocellulosic biomass. Here, the cisaconitic acid decarboxylase gene was expressed in a heterologous method to synthesize itaconic acid. This engineered strain was able to produce itaconic acid from lignocellulosic biomass.

Likewise, itaconic acid was also produced from biomass hydrolysate using Asphergillus strains in another previous study. Here, acid and enzymatic hydrolyzates were analyzed to produce itaconic acid. After submerged fermentation was done with corncob nydrozylate by the fungus Aspergillus oryza, high yield itaconic acid production was observed. This study also shows the potential simultaneous saccharification and fermentation of the biomass for itaconic acid production.