Role of Raffinose Family Oligosaccharides in Respiratory Metabolism During Soybean Seed Germination

Abstract

Role of raffinose family oligosaccharides (RFOs), sucrose and lipid in respiration metabolism during soybean seed germination were investigated to determine appropriate method for producing soybean sprouts containing high amount of RFOs. Soybean seed were soaked into 50 μM 1-deoxygalactonojirimycin (DGJ), which is a specific α-galactose inhibitor, for 90 minutes before and after germination preparation phase (GPP). Soybean seed without DGJ treatment was used as control. The growth rate, respiration rate, respiratory quotient, fatty acids and saccharides contents were measured during cultivation at 20℃. When DGJ was applied before GPP, the degradation of RFOs was significantly reduced, moreover the growth rate and respiration rate were suppressed due to the alternation of respiratory substrate from glucose to lipid in GPP. However, in the DGJ application after GPP, no difference was found from control although RFOs breakdown was functionally inhibited in subsequent radicle elongation phase (REP). These results suggest that RFOs are essential only in GPP as a source of respiratory substrate and lipids play the main role in respiration during REP. Therefore, prevention of RFOs degradation after GPP could be useful to maintain high amount of RFOs in soybean sprouts.