Production of Glucaric Acid from Hemicellulose Substrate by Rosettasome Enzyme Assemblies
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Hemicellulose biomass is a complex polymer with many different chemical constituents that can be utilized as industrial feedstocks. These molecules can be released from the polymer and transformed into value-added chemicals through multistep enzymatic pathways. Some bacteria produce cellulosomes which are assemblies composed of lignocellulolytic enzymes tethered to a large protein scaffold. Rosettasomes are artificial engineered ring scaffolds designed to mimic the bacterial cellulosome. Both cellulosomes and rosettasomes have been shown to facilitate much higher rates of biomass hydrolysis compared to the same enzymes free in solution. We investigated whether tethering enzymes involved in both biomass hydrolysis and oxidative transformation to glucaric acid onto a rosettasome scaffold would result in an analogous production enhancement in a combined hydrolysis and bioconversion metabolic pathway. Three different enzymes were used to hydrolyze birchwood hemicellulose and convert the substituents to glucaric acid, a top-12 DOE value added chemical feedstock derived from biomass. It was demonstrated that colocalizing the three different enzymes to the synthetic scaffold resulted in up to 40 % higher levels of product compared to uncomplexed enzymes.
KeywordsHemicellulose Lignocellulases Glucaric acid Enzyme nanoassembly
We thank Bruce Mackey and Linda Whitehand for consultations on the statistical design of the experiments. This work was supported by the United States Department of Agriculture (CRIS 2030-41000-054-00) and National Institute of Food and Agriculture (Grant 2012-03998). The mention of firm names or trade products does not imply that they are endorsed or recommended by the US Department of Agriculture over other firms or similar products not mentioned. USDA is an equal opportunity provider and employer.
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