Effect Of Gas Phase Oxygen On Metabolic Regulation Of Postharvest Ganoderma Lucidum

Ganoderma lucidum is a famous institution of higher medicinal fungi,has a long history.The secondary metabolites of G.lucidum,Ganoderma acid?GA?and Intracellular polysaccharide?IPS?,were important active substances and have attracted the attention of researchers.At present,there were many methods for increasing the yield of GA and IPS,including optimization of culture conditions,and overexpressing key enzyme genes.However,studies on postharvest physiology and active substance metabolism of G.lucidum have not been reported.Therefore,in this paper,takes the postharvest G.lucidum mycelium and postharvest fruit body as research objects.To investigate the effects of different concentrations of oxygen on the biomass,physiological activity,metabolite content and expression of key enzymes in the synthesis pathway of G.lucidum.Compared with normal culture conditions,the content of metabolites of postharvest G.lucidum mycelium preserved in different concentrations of oxygen was significantly improved.Especially in the 60%oxygen concentration,the IPS content was 28.68 mg/100 mg dry weight,1.4 times that under normal culture conditions.The total GA reached3.64 mg/100 mg dry weight,which was 1.5 times that under normal conditions.The contents of the four monomeric GA?GA-Mk,GA-T,GA-S,GA-Me?were also increased to varying degrees,339.4,713.8,416.8 and 373.8?g/100 mg dry weight,respectively.The postharvest G.lucidum fruiting body had a GA content of 0.83 mg/100 mg dry weight at 80%oxygen concentration,which is 32%higher than normal conditions.The content of GPS is 12.1mg/100mg,which is 1.4 times under normal conditions,and the content of four Ganoderma lucidum monomers also increases to varying degrees.After harvesting G.lucidum stored in different oxygen concentrations,the physiological state had also undergone great changes.For postharvest G.lucidum mycelium,different oxygen concentrations can affect the growth of postharvest G.lucidum mycelium and some antioxidant enzyme activities.The content of MDA?malondialdehyde?and H₂O₂?hydrogen peroxide?in 60%oxygen was only equivalent to75%of the control group,while SOD?superoxide dismutase?,CAT?catalase?and POD(over The enzyme activity of the oxide enzyme increased to 2.7 U/g FW,99 nmol/min/g FW,and 114 U/g FW,respectively.The postharvest G.lucidum fruiting bodies were also stored in 80%oxygen for 5 days.The enzyme activities of SOD,CAT and POD were 1.7,2.5 and 1.8 times of the control group,respectively.In order to study the effect of gas phase oxygen on the secondary metabolism of postharvest G.lucidum,the expression of key enzyme genes in the biosynthesis pathway of GA and IPSwas analyzed by real-time PCR.The results show that gas phase oxygen can increase the expression of some key enzyme genes in postharvest Ganoderma lucidum.In 60%oxygen,the expression levels of key enzyme genes HMGR,SQS,LS and SE of G.lucidum mycelium after harvest were 3.8,2.3,2.1 and 1.9 times of the control group,respectively.The expression levels of UGP and GLS were 2.5,1.5 and 2.2times of the control group,respectively.In 80%oxygen,the expression levels of HMGR,SQS,LS and SE in postharvest G.lucidum fruit bodies were 1.9,2.0,2.2 and 2.8 times,respectively,under normal storage conditions.The expression levels of PGM,UGP and GLS genes were 3.2 times,2.3 times and 3.0 times,respectively,under normal storage conditions.In this paper,the effects of gas phase oxygen on the metabolic regulation of postharvest G.lucidum were studied.The effects of different oxygen concentrations on the yield of metabolites of G.lucidum mycelium and G.lucidum fruit bodies,physiological activities of G.lucidum cells and expression of some key enzyme genes were investigated.For future studies on the regulation of gas phase oxygen on the metabolism of other higher medicinal fungi.