Production of D-xylonic acid from hemicellulose using artificial enzyme complexes

Authors: Lee, Charles; Kibblewhite, Rena; PAAVOLA, CHAD - National Aeronautics And Space Administration (NASA); Orts, William; Wagschal, Kurt

Submitted to: Journal of Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2016
Publication Date: 1/28/2017
Citation: Lee, C.C., Kibblewhite, R.E., Paavola, C., Orts, W.J., Wagschal, K.C. 2017. Production of D-xylonic acid from hemicellulose using artificial enzyme complexes. Journal of Microbiology and Biotechnology. 27(1):77–83 doi: 10.4014/jmb.1606.06041.

Interpretive Summary: The world’s continued reliance on fossil fuels to supply our chemical feedstock and fuel needs is unsustainable due to environmental damage from extraction, climate change from combustion, and eventual resource depletion. It is estimated that there are greater than 220 billion tons of lignocellulosic biomass available globally, which represents a tremendous renewable source for society’s chemical demands. However, the difficulty and costs associated with processing the lignocellulose make the transition from fossil fuels to this renewable resource very challenging. Therefore, much attention has been placed on efficiently deriving value-added byproducts from all fractions of biomass. We created artificial enzyme assemblies that had enhanced levels of biomass conversion into the value-added product xylonic acid. This multipurpose chemical has a variety of potential uses, including as a concrete dispersal agent and a building block of copolyamide polymers. Furthermore, it has been utilized as a precursor for other chemicals, such as 1,2,4-butanetriol which is also a valuable feedstock chemical involved in the synthesis of plasticizers, polymers, and medical precursors for drug.

Technical Abstract: Lignocellulosic biomass represents a potentially large resource to supply the world’s fuel and chemical feedstocks. Enzymatic bioconversion of this substrate offers a reliable strategy for accessing this material under mild reaction conditions. Due to the complex nature of lignocellulose, many different enzymatic activities are required to function in concert to perform efficient transformation. In nature, large multienzyme complexes are known to effectively hydrolyze lignocellulose into constituent monomeric sugars. We created artificial complexes of enzymes, called rosettazymes, in order to hydrolyze glucuronoxylan, a common lignocellulose component, into its cognate sugar D-xylose and then further convert the D-xylose into D-xylonic acid, a DOE top-30 platform chemical. We demonstrated that tethering our enzymes in a complex resulted in significantly more activity than the same amount of enzymes free in solution. We also investigated the effect of varying the enzyme composition on overall product formation and level of complex-related activity enhancement.