(365b) Acid Extraction of the Phytate from Various Corn Ethanol Coproducts

The bioethanol industry is rapidly developing in the U.S, with dry milling process as the major method. This process therefore produces an increasing amount of coproducts such as distillers’ dried grains with solubles (DDGS). DDGS contains large amounts of important nutrients and high levels of phytate, and is widely used in animal diets of livestock industry such as dairy, beef, swine, and poultry. However, the phytate in DDGS cannot be directly digested by nonruminant animals and large quantities of phytate phosphorus (P) are discharged into the soil with the animal wastes. This can potentially cause excessive P accumulation in soil, surface and underground water bodies. On the other hand, phytic acid (PA), the acid form of phytate, has been confirmed for its beneficial effects on human health as a nutritional compound. Effective extraction of phytic acid from corn ethanol coproducts will bring revenue to the bioethanol industry by generating the more value-added product.

This study aims at optimizing PA extraction from intermediates of the corn ethanol coproduct DDGS, including concentrated distillers stillage (CDS) and wet distillers grain (WDG). PA is extracted with various HCl level (pH between 1.0 to 4.0), at different temperatures (35 and 50 ^oC), extraction time (1 to 6 h), and with different ratios of liquor to solids (2:1 to 10:1). The extracted PA concentrations were determined via spectrophotometry method (ferric ion and sulfosalicylic acid) after purification by the anion exchange resin to remove heteroion such as phosphate ion. The optimization study would give the best reaction conditions for PA extraction in terms of pH, extraction time, temperature, ratio of liquor to solids.

When extraction condition optimized, a 1-L scale reactor was designed and used to recover PA from the extracted solution. The pH value of the solution was adjusted to 7.0 by adding NaOH, and phytate was then precipitated with Ca(OH)₂ as calcium phytate solid by sedimentation, centrifuge, and oven-drying. The whole process produced about 5 to 10 g of phytate when undiluted CDS used as feedstock.