1a. Objectives (from AD-416):
Develop new hulled and hulless barley lines having traits desirable to enhance production of fuel ethanol and add value to the animal feed coproduct, DDGS; engineer commercial ethanol yeasts to detoxify mycotoxins such as DON that are sometimes found on barley kernels in wet growing years and that would be detrimental to animals who ate the resulting ethanol coproduct, DDGS, derived from that grain and; evaluate hull removal strategies to reduce DON levels in raw barley kernels prior to fuel ethanol production as another way to reduce levels of DON in DDGS.
1b. Approach (from AD-416):
Virginia Tech breeders will send new barley varieties to us for evaluation. Varieties containing high levels of starch, beta-glucan, and protein will be fermented to ethanol and the coproduct, DDGS. Varieties producing the highest ethanol yields and DDGS with highest protein will be selected as top candidates. Virginia Tech researchers will transform commercial ethanol yeasts with a 3-O-acetyltransferase (TRI101) enzyme, which catalyzes the acetylation of DON at the third carbon, reducing the toxicity of DON by two orders of magnitude. We will test the ability of these yeasts to detoxify DON during a series of small-scale ethanol fermentations using raw barley grain containing different levels of DON. We expect the enzyme to detoxify DON during simultaneous saccharification and fermentation. It is expected that the use of these transgenic yeasts during fermentation will add additional value by the production of barley DDGS with low DON levels. ERRC researchers will remove barley hulls using several different types of mills (pearling, roller milling, precision impact mill) to determine if removal of hull will result in barley kernels with lower DON levels.
3. Progress Report:
Levels of the mycotoxin deoxynivalenol (DON) were determined for harvested grain from selected barley varieties and elite experimental lines grown and harvested in the 2011 growing year. In 2011, we proved that DON content of barley kernels survives the process used to convert barley to ethanol and winds up in the DDGS fraction, which is used for animal feeds. This study was the first to confirm that DON is concentrated in DDGS during fuel ethanol production from barley. This result underscored the importance of developing strategies to reduce DON during the fermentation process. Also in 2011, we showed that a recombinant Saccharomyces yeast, containing novel DON detoxification genes was able to simultaneously produce ethanol and detoxify DON during barley ethanol fermentations. The results showed that DON could be significantly reduced during fuel ethanol fermentation (9.2% to 55.3% of DON was converted to a less toxic derivative of DON). This work was published and noted in the FY 2011 Annual Report. Since that time, the article has been accessed over 2000 times by researchers around the world. In FY 2012, we began experiments to lower the levels of DON in barley grain by dry fractionation of the kernels, prior to fuel ethanol and DDGS production. Hulls were removed from a set of hulled barley grain lots using scarification, precision de-hulling, and improved roller milling methods. DON is currently being quantified in the resulting fractions (untreated kernels with hulls, kernels without hulls, and hulls without kernels). The results are showing that this process significantly lowers the amount of DON in the fermentable parts of the barley kernel. A new publication on this work is in preparation.