Production of a Zero Calorie Sweetener L-arabinose from Biomass D-Xylose by an Enzyme Cocktail

A new high-value product zero calorie sweetener L-arabinose has been identified because it may be produced from the D-xylose-rich aqueous biomass intermediate stream at low costs. L-arabinose is an FDA approved healthy sweetener with dual functions as a sucrase inhibitor and a prebiotic, but its current high price ($30/kg) prevents wide use. The co-production of high-value products such as L-arabinose will be essential to the economic success of next generation biorefineries. The goal of this project is to decrease L-arabinose production costs by a factor of 10-15 via synergistic efforts in feedstock selection, novel biocatalysis, and product separation. Here, we will use a synthetic enzymatic pathway to convert the D-xylose in aqueous biomass hydrolysate to high concentration L-arabinose. This three-enzyme biocatalysis can be accomplished in an aqueous solution without the input of energy, chemicals, and cofactors. Also, a selective yeast fermentation will be used to remove other sugars for easy L-arabinose purification. The objective of this STTR I project to validate the feasibility of the isomerization of D-xylose to L-arabinose via this three-enzyme pathway.In this Phase I project, we will discover a promiscuous homolog of L-ribulose 5- phosphate 4-epimerase that works on L-ribulose, increase specific activities of L-ribulose 4- epimerase mutants by protein engineering, validate the production of L-arabinose from D-xylose, and file a provisional patent disclosure based on experimental data.Low-cost L-arabinose as a sucrose neutralizer could have a potential market of up to $10 billion/year. Its addition in numerous food and drinks will decrease risks of obesity, type 2 diabetes, cardiovascular diseases, hypertension, and cancer. The co-production of L-arabinose from D-xylose, along with the production of advanced biofuels from cellulose, will improve the economic viability of next generation biorefineries greatly and efficiently utilize abundant renewable biomass resources. The success of this project will promote the concept of cell-free biocatalysis as a green and low-energy intensive manufacturing process.