Peroxide/Lime Pretreatment of Wheat Straw and Reduced Bacterial Contamination During Ethanol Fermentation

Researchers from the National Center for Agricultural Utilization Research of the Agricultural Research Service (ARS), United States Department of Agriculture (USDA), report some latest findings in their research on ethanol production from wheat straw. They found two pretreatment methods which did not produce compounds known as "fermentation inhibitors" and were effective in increasing ethanol yields. These pretreatments were the addition of alkaline peroxide and lime.

Pretreatment is one of the first steps in the conversion of lignocellulosic biomass to ethanol. It removes the lignin wrapping around the biomass, to expose the hemi-cellulose fibers. The exposed fibers can then be degraded into simple sugars for ethanol fermentation. Conventional pretreatments using acid or alkali often produce compounds which inhibit the ethanol fermentation step ("fermentation inhibitors", such as furfural). Alkaline peroxide and lime pretreatments were successfully done without the production of such inhibitors. Ethanol yields for alkaline peroxide and lime pretreatments were 93 gallons per ton of wheat straw and 83 gallons per ton of wheat straw, respectively.

The scientists also report some progress in the analysis of bacterial contamination during ethanol fermentation. According to USDA-ARS microbiologist, Ken Bischoff, "chronic infections can reduce ethanol yields from 2 to 4 percent, which is a lot at a plant that produces 100 million gallons of ethanol a year." A shake-flask model for simulatng bacterial contamination during ethanol fermentation was developed, which can be used for helping the ethanol industry find strategies to control bacterial contamination in their ethanol fermentation plants.

Related information: Modelling of bacterial contamination during ethanol fermentation http://ddr.nal.usda.gov/bitstream/10113/29908/1/IND44187615.pdf