Study On The Variation Of Moisture In The Cultivation Substrates Of Lentinula Edodes And Its Effect On The Content Of Lenthionine

Shiitake mushroom[Lentinula edodes（Berk）.Pegler]is a sulfur-rich mushroom,which was known for its rich taste,special flavor,and high nutritional value.With the development of society,it is imperative to develop highly efficient L.edodes cultivation technology as well as a high-quality L.edodes production process.However,limited by the backwardness of basic research of L.edodes cultivation,the innovation of L.edodes cultivation technology and the development of social demand of L.edodes become unbalanced.Therefore,advancing the basic research of L.edodes is an immediate need for the development of the L.edodes industry.This study focuses on the basic composition of L.edodes cultivation substrate,solves the problem of water detection and water supply of the substrate,and investigates the mechanism of water regulation on flavor substances of L.edodes,so as to make a theoretical pavement for developing cultivation technology that is favorable to the growth and improvement of flavor quality of L.edodes.1.The study revealed that moisture is the main factor that dominates the variation of the three-phase structure of L.edodes cultivation substrate.The relationship between three-phase structure index（TPSI）and L.edodes biomass was fitted by Rational model,and there was a linear relationship between L.edodes biomass and TPSI when the value of TPSI was lower than 23.3.Three types of water containing four proton components in the cultivation substrate were identified based on distributed exponential curve fitting of transverse relaxation（T₂）,namely,bound water T_2b,free water T_21aand T_21b,and bulk water T₂₂.L.edodes had the best growth efficiency on elm（59%moisture content）,peanut shell（52%moisture content）and apricot（56%moisture content）substrates,all of which were free water-filled and bulk water-absent,respectively,which makes the proton analysis based on LF-NMR spectroscopy can provide new insights into the moisture content of wood-rot fungal cultivated substrates.2.Secondly,in this study,the dynamic water monitoring of cultivated substrates for L.edodes growth over a long period by LF-NMR revealed that the water dissipation in cultivated substrates was mainly due to the decrease in signal intensity of T_21bfraction.Further,it was found that L.edodes under 10%SAPs condition possessed the maximum growth efficiency by 142%.10%SAPs condition increased the cellulase and laccase activities of L.edodes and their related synthetic genes were all up-regulated.However,the content of its key flavor substance,L.edodes extract,decreased by about60%,the activity of cysteine sulphoxide lyase（LECSL）andγ-glutamyl transpeptidase（GTT）decreased with the increase of SAPs addition,and the transcriptional activities of their related genes（LECSL-1,LECSL-2,LECSL-3,LECSL-4,LECSL-5,GTT-1,GTT-2,GTT-3,GTT-4,GTT-5,GTT-6）all showed a decrease in transcriptional activity.After that,the results of LF-NMR monitoring profiles of the water retention agent addition group showed that 10%SAPs addition was effective in reducing the total water dissipation in the cultivated substrate,mainly by maintaining the peak area of T_21bstable and not causing the appearance and elevation of T₂₂.These results suggest that 10%SAPs can improve the growth efficiency of L.edodes by maintaining the stability of free water T_21b.3.This study also revealed that water deficit stress is also involved in regulating the anabolism of L.edodes essence,a flavor substance of L.edodes.We analyzed the regulatory role of cysteine（L-Cys）synthesized by the cysteine-β-lyase（CSE-1）gene involved in the metabolism of L.edodes essence under drought stress.The results showed that 10%polyethylene glycol（PEG）-induced water deficit stress promoted the accumulation of lenthionine,in cells,in addition to the significant up-regulation of the enzyme activity levels of GTT and LECSL,key enzymes in the lenthionine metabolic pathway.Further studies showed that water deficit stress-induced the expression of CSE-1,a key gene for L-Cys synthesis,and promoted the efficiency of intracellular L-Cys synthesis.Our results also showed that inhibition of CSE enzyme activity or silencing of CSE gene with inhibitors under water deficit conditions significantly reduced intracellular L-Cys content and lenthionine accumulation,but the inhibitory effect of lenthionine synthesis disappeared after exogenous back supplementation of L-Cys.These results suggest that lenthionine synthesis in L.edodes under water deficit stress conditions is dependent on cysteine.In summary,this study found a linear relationship between TPSI of L.edodes cultivation substrates and the growth level of L.edodes.Secondly,an optimal water content monitoring system for L.edodes based on the principle of the LF-NMR technique was developed.Also,the growth of L.edodes was promoted by 10%SAPs to maintain the stability of free water T_21b.Besides,it was found that water deficiency could activate CSE-1 activity,which promoted the synthesis of lenthionine by up-regulating the synthesis of L-Cys.This study helps to advance the development of efficient cultivation of L.edodes and provides a realistic reference for flavor quality optimization of L.edodes from a physiological perspective.