Distribution of phytic acid and associated catabolic enzymes in soybean sprouts and indoleacetic acid promotion of Zn, Fe, and Ca bioavailability

Phytic acid is involved in storage of phosphorus and minerals in soybeans. The effects of 6 basic plant hormones on phytic acid degradation were investigated. After 6 days of germination, phytic acid contents in soybean sprouts decreased by 70%, compared with day 0 soybeans. Zn and Fe bioavailability of 6-day-old germinating soybean both significantly increased (p < 0.05), by contrast, Ca bioavailability decreased compared with controls. Phytic acid was detectable only in cotyledons of soybean sprouts during germination. In germinating soybeans, 39.19-45.85% and 54.15-60.81% of phytase existed in embryos and cotyledons, respectively. Unlike phytase, acid phosphatase was present mainly in cotyledons (92.57-97.51%). Among the 6 hormones, 50 mg/L indoleacetic acid (IAA) brought the highest degradation value to phytic acid content, meanwhile, Zn, Fe, and Ca bioavailability of IAA-treated soybeans were significantly (p < 0.05) improved, compared with that of the control, respectively.