Designer Sorghum: Combining the High Digestible and Waxy Grain Traits for Improved Nutrition, Bioethanol, Beer, Food and Feed Products.

Sorghum (Sorghum bicolor (L). Moench) is an important crop in most parts of the world. It is used for human consumption in parts of Africa and Asia and for animal feeding mainly in the United States. Our goal is to develop sorghum cultivars that combine a high endosperm protein digestibility (HD) trait with a high amylopectin (waxy) starch trait that would improve the grain's endosperm matrix for bioethanol conversion and brewery applications. The HD trait also confers a 100% increase in limiting amino acid lysine and others. As such, we have also found that the grain distiller's feed following fermentation also has twice the lysine content. Sorghum has low levels of protein digestibility when compared to other cereals. The reason for the low poor protein digestibility is thought to be due to high cysteine residue composition and high degree of disulphide bonds found in the (- kafirins that reside on the periphery of the kafirin containing protein bodies. In previous research, two QTLs were found to be associated to protein digestibility, one QTL negatively affecting digestibility and another one positively affecting QTL. Waxy sorghums have little or no linear starch (amylase) and a highly branched amylopectin starch content. Waxy sorghums gelatinize more rapidly, at lower temperatures and are more susceptible to enzyme hydrolysis and hence should be better for bioethanol conversion. These modifies endosperm traits very significantly reduce the temperature and duration at elevated temperatures needed to solubilize the grain starch for hydrolytic enzyme access and conversion to fermentable sugars. The new sorghum hybrids will also provide distillers an increased income through the improved essential amino acid and nutrition quality of the high protein distillers dried grain feed product.