Researchers Develop Integrated Process to Streamline Production of a Key Bio-Based Polymer

Achievement date: 

Research teams at the Center for Biorenewable Chemicals (CBiRC), an NSF-funded Engineering Research Center (ERC) headquartered at Iowa State University (ISU), have demonstrated an integrated process that streamlines generation of a bio-based polymer (polymers are important chemical compounds, like nylon and other plastics, used to make everyday products). In this case, streamlined generation of a new polymer similar to nylon resulted from using a combined bio- and electrocatalytic process. 


This work demonstrates a strategy to bridge the current gap between biological and chemical catalysis in biorefineries, which convert biomass feedstocks to final products that formerly required petroleum inputs. Using biomass instead of petroleum is expected to grow a more sustainable chemical industry, alleviate concerns about fossil resources, and revitalize the chemical industry by providing building blocks with new functionalities.


Since the U.S. Department of Energy’s report on top value-added chemicals from biomass, extensive research has been carried out to establish biological, chemical, or hybrid pathways for converting cellulosic sugars, which are renewable resources for biochemical and biofuels industries. Over the past few years, it has become evident that diversification of building blocks requires the combination of biological and chemical transformations (i.e., biomass is first biologically converted using microbes to platform molecules, which are further diversified using chemical catalysis). Unfortunately, ideal biorefinery pipelines—from biomass to the final products—are currently disrupted by the gap between biological conversion and chemical diversification.

Muconic acid (MA), a six-carbon unsaturated dicarboxylic acid, has been a target fermentation molecule for CBiRC's Thrust 2 research. Given its structural similarity to adipic acid, MA is a promising platform molecule for the production of several precursors that serve as building blocks for the formation of synthetic polyamides, like Nylon-6,6. Thrust 2 researchers engineered a strain of S. cerevisiae with the highest MA titer from glucose fermentation reported in literature (559 mg L-1). Also, technology developed by CBiRC's Thrust 3 researchers allowed the electrocatalytic hydrogenation of MA to 3-hexenedioic acid (3-HDA) directly in the fermentation broth. The use of lead as a robust base metal catalyst removed the need for expensive separation, enabling a seamless streamlining of the production pipeline. The work resulted in a featured publication in Angewantde Chemie International Edition.

The researchers anticipate that the integrated strategy (see figure) will facilitate incorporation of fermentation and catalytic hydrogenation for a broad range of reactions. Production of 3-HDA through electrocatalysis enabled the production of a family of new, unsaturated polyamides-6,6 (UPA) with similar physicochemical properties to that of Nylon-6,6 obtained from petrochemical adipic acid. The UPA obtained from this work possesses an advantage over current nylon: i.e., the inserted unsaturation can be readily substituted by other chemical functional groups, therefore allowing fine-tuning of the properties of the resulting polyamide.