Abstract
Soybean meal (SBM) is the world’s largest source of animal protein feed due to its high protein content, balanced amino acid profile, availability, and cost-effectiveness. However, its nutritional value can be enhanced by addressing antinutritional factors (ANFs) present in SBM. This presentation aims to summarize our research efforts to significantly boost the nutritional value of SBM by reducing or eliminating some of these antinutritional factors through genetic manipulation. Antinutritional factors are compounds that interfere with the digestion and absorption of nutrients. In soybean meal, these include trypsin inhibitors, allergens (β-conglycinin), phytic acid, lectins, and oligosaccharides. Trypsin inhibitors reduce protein digestibility by inhibiting the action of the enzyme trypsin, while β-conglycinin can cause inflammatory responses, compromising nutrient absorption. Soybean seeds contain two major classes of proteinaceous inhibitors: 1) Kunitz-trypsin inhibitors (KTi), which inactivate the digestive enzyme trypsin, and 2) Bowman-Birk inhibitors (BBi), which inactivate both trypsin and chymotrypsin digestive enzymes. β-conglycinin, the abundant 7S seed storage protein of soybean, is composed of α’, α, and β-subunits, all of which have been demonstrated to be major allergens. We have utilized genetic engineering technology to lower the levels of ANFs in SBM. In addition to identifying naturally occurring KTi mutants, we have employed CRISPR/Cas9 gene editing to create mutations in BBi genes, drastically lowering the trypsin inhibitor content in soybean seeds. We have also successfully utilized RNAi technology to generate transgenic soybeans devoid of all three subunits of the allergenic β-conglycinin. The generation of transgenic soybeans lacking trypsin inhibitors and β-conglycinin would significantly boost the nutritional value of SBM. Such soybeans could become an even more valuable feed ingredient in the global animal agriculture industry.