Study on the Effect of Potassium and Manganese on the Content of Mycelium Polysaccharide and Activities of Key Enzymes Related to Polysaccharide Biosynthesis of Lentinula edodes
[Objective]This study was conducted to explore the effects of potassium(K+)and manganese(Mn2+)on the mycelium polysaccharide productions,relative expression of key enzyme genes and en-zyme activities in polysaccharide synthesis.[Method]The effects of K+and Mn2+on mycelium growth,intracellular polysaccharide(IPS),extracellular polysaccharide(EPS),and total polysaccharide(TPS)productions were studied using the main cultivar Lentinula edodes'Xin808'.Five different metal concen-trations and four different metal adding times were employed in this study.The activities of three key en-zymes involved in polysaccharide biosynthesis,glucose phosphate isomerase(PGI),glucose phosphate mutase(PGM),and uridine diphosphate glucose focal phosphorylase(UGP),as well as the transcrip-tional expression levels of their coding genes,were also determined.[Result]When using the TPS con-tent as an indicator,the optimal induction concentrations of K+and Mn2+were 1 000 mg/L and 600 mg/L,respectively,with the optimal induction time occurring after 7 days of shaking upon metal ions addition.Analysis on the dynamic changes showed that the polysaccharide contents were consistently lower under K+treatments compared to the control throughout the incubation period.In the initial culture stage,the activity of PGI was inhibited while the activities of PGM and UGP were enhanced.However,in the later culture stage,the activities of PGM and UGP were also inhibited.The TPS content reached its maximum value when cultured for 60 d under Mn2+treatment,coinciding with improved activities of PGM and UGP.Under K+and Mn2+treatments,all three genes showed relatively higher expression levels at early culture stage.Correlation coefficient analysis showed that the EPS and TPS contents significantly(P<0.05)corre-lated with enzyme activities of PGM and UPG under Mn2+treatment.[Conclusion]Adding 600 mg/L of Mn2+in the fermentation medium improves the yield of polysaccharide,while the addition of 1 000 mg/L of K+suppresses the polysaccharide yield.
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