Accumulation of γ‐aminobutyric acid in soybean by hypoxia germination and freeze–thawing incubation

Abstract BACKGROUND γ ‐Aminobutyric acid ( GABA ) can be synthesised by the GABA shunt and polyamine degradation pathway in plants under hypoxia stress and lower temperature. The hypoxia germination freeze–thawing incubation was used as a new technique for accumulating more GABA in soybean. RESULTS Results showed that glutamate decarboxylase ( GAD ) and diamine oxidase ( DAO ) activity as well as GABA content increased during germination within 24 h under hypoxia. However, the contents of dry matters and protein decreased. When the hypoxia‐treated sprouts were frozen at −18 °C for 12 h and thawed at 25 °C for 6 h, GABA content increased drastically to 7.21‐fold of the non‐frozen sprouts. Subsequently, the freeze–thawing sprouts were ground into homogenates and incubated. GABA content was 14.20‐fold of the only‐soaked seeds when homogenates was incubated at 45 °C for 80 min within 400 µmol L −1 pyridoxine ( VB 6 ) ( pH 6.5). CONCLUSION The hypoxia germination freeze–thawing incubation was an effective method for accumulating GABA in soybean. During incubation, DAO was more important for GABA formation in homogenate of germinated soybean compared with GAD . © 2015 Society of Chemical Industry