Mechanism Of Calcium Lactate And Gibberellic Acid On Regulating Phytic Acid Degradation Of Soybeans During Germination

Phytic acid,as a phosphorus storage vault,provides phosphorus for seeds germination.It is difficult for humans and monogastric animals to digest and absorb phytic acid.Meanwhile,phytic acid is considered as an anti-nutritional factor because of its strong chelation to proteins and minerals.During seed germination,endogenous phytase and phosphatase are activated to degrade phytic acid into lower inositol phosphates which can reduce the anti-nutritional effects and is beneficial to human health.Soybean is a popular agri-food in China,but phytic acid accounts for 1%dry mass of soybean seed.Therefore,phytic acid in soybean is worth further developing and studying.This study focused on regulating the degradation of phytic acid in soybeans during germination using exogenous calcium lactate and gibberellic acid and revealing the relevant mechanism of action,the main content are as follows:Soybeans were sprayed with 0.27 mM calcium lactate during four-day germination in the darkness,and the phytic acid degradation and the variation of the main nutrient content of germinating soybeans were studied.The results showed that the phytic acid in soybean sprouts was degraded significantly and the availability of zinc and iron were improved.Soluble protein and soluble sugar content decreased gradually,while the content of free amino acids rose.The content of crude proteins basically kept steady,while the amino acids composition varied.Among 17 amino acids,the content of aspartic acid(Asp)and histidine(His)increased with the germination time,and the content of other amino acids decreased.Calcium lactate facilitated the accumulation of Asp and valine(Val),but decreased the content of other amino acids.In addition,the content of total phenolics and the antioxidant capacity increased.Spraying soybean sprouts with a low concentration calcium lactate could promote growth and phytic acid degradation,and enhance the nutritional properties of soybean sprouts.Soybeans were sprayed with 0.27 mM calcium lactate and 0.27 mM calcium lactate plus lanthanum chloride(LaC13)during four-day germination in the darkness,and the relevant mechanism of calcium lactate on phytic acid degradation in soybean sprouts was studied.The results showed that the enzyme activity related to phytic acid degradation increased.Phytic acid content decreased and the availability of phosphorus increased under calcium lactate treatment.In addition,the energy metabolism was accelerated by calcium lactate.The energy status and energy metabolism associated enzyme activity also increased.The results were opposite to calcium lactate treatment under calcium lactate plus LaCl3.The transmembrane transport of calcium was inhibited by La3+ and concentrated in intercellular space or between the cell wall and cell membrane,and the gene expression of phytic acid degradation-associated enzymes did not vary in accordance with their enzyme activity.The application of calcium lactate significantly promoted the transference and absorption of soybean sprouts,and increased the rate of substance metabolism and energy metabolism.Calcium lactate increased the rate of phytic acid degradation by enhancing growth,phosphorus metabolism,and energy metabolism.Soybeans were sprayed with 0.27 mM calcium lactate,and 1?M gibberellic acid(GA)and 10 mg/L endogenous GA synthesis inhibitor paclobutrazol(PAC)were added exogenously during four-day germination in the darkness.The effects of GA on the changes of physiological and biochemical,phytic acid degradation,the activity of phytic acid degradation-associated enzymes,the activity of phosphoinositide-specific phospholipase C(PI-PLC)and its gene expression were studied.The results showed that calcium lactate plus gibberellic acid treatment promoted the growth state,hormone metabolism and phytic acid degradation in germinating soybeans.At the same time,the availability of phosphorus,the activity of phytic acid degradation-associated enzyme and PI-PLC increased.However,the relative gene expression of phytic acid degradation-associated enzymes did not vary in accordance with their enzymes activity.The results revealed that GA could mediate the transport and function of calcium and a series of physiological and biochemical changes to regulate phytic acid degradation of soybean sprouts.GA played an important role in signal transduction of Ca2+.It promoted the phytic acid degradation and phosphorus metabolism,and maintained the exuberant vital activities of soybean sprouts via regulating the absorption and release of Ca2+ and a series of physiological and biochemical changes.