Developments in enzymatic soy processing to increase yield and value

Enzymatic processing of soybeans presents a promising alternative or supplement to the existing methods. The new approach minimizes the use of thermal and mechanical treatments and organic solvent extraction, and it enabled, with a single enzymatic step, production of undenatured protein and intact oil bodies and conversion of potentially indigestible, antinutritional oligomeric and polymeric carbohydrates to readily assimilable monomeric sugars. Additionally, it maximizes the overall value of soybeans by reducing unutilized byproducts and broadening processing capabilities beyond traditional methods with greater product selection flexibility. But the carbohydrates in soybeans are complex; so, the enzyme used in this new processing needs to have a wide range of carbohydrase activities including at least cellulase, xylanase, pectinase, α-galactosidase, and invertase, while minimizing protease to reduce protein loss. The new approach involves two main steps: production of effective enzyme and enzymatic processing of cracked, dehulled soybean particles into separate streams of oil bodies, protein, and carbohydrate hydrolysate. Enzyme production was studied with submerged fermentation and solid-state fermentation (SSF) using soybean hulls as the solid substrate. SSF was found to give higher enzyme yield and productivity. The limiting enzyme activities were identified by mixing soybean particles with different enzymes produced using various SSF conditions and then correlating the enzymatic processing effectiveness with all carbohydrase activities. The limiting-enzyme identification guided subsequent SSF to maximize these limiting activities, while keeping protease low, through optimizing nutrient supplementation, harvesting time, and other operating conditions. Simultaneously, the efficiency and yield of enzymatic soy processing technology were enhanced by optimizing processing conditions including use of pulsed sonication. Results and insights gained from the studies will be presented.

*This project is funded by the United Soybean Board. Project #2422-106-0201 and #2522-106-0102. The study has not been peer-reviewed yet.