Technoeconomic Analysis of Conversion of Corn Fiber to Ethanol Using Engineered Thermophilic Bacteria

Corn fiber - containing arabinose, xylose, and cellulose in roughly equal amounts and not currently fermented - could in principle be converted to ethanol with little or no loss in the value of residual solids as an animal feed. The challenge is to solubilize and ferment this unusual biomass feedstock in a cost-effective manner. We present data indicating that corn fiber can be nearly completely solubilized by Clostridium thermocellum whereas solubilization yields using controls with industry-standard fungal cellulase are on the order of 50%. Data on conversion of arabinose and xylose by engineered strains of Thermoanaerobacter thermosaccharolyticum will also be presented.

In the main part of this presentation, we present a technoeconomic analysis of thermophilic conversion of corn fiber. In particular, we analyze the parametric impact of key performance parameters on payback period, including solubilization yield (fractional sugars solubilized), fermentation yield (ethanol produced per sugar fermented), and ethanol titer. Integrated separation of a dilute ethanol stream resulting from thermophilic corn fiber fermentation with a larger flow of more concentrated ethanol produced from corn starch fermentation is analyzed. It is concluded that economic viability can be achieved at lower ethanol titer in a bolt-on configuration as compared to a stand-alone configuration. Results support corn fiber conversion as a low-capital/high return point-of-entry for industrial application of engineered thermophilic microbes.