Study On Oxalate Metabolism Of The Response Of Lentinula Edodes To Ambient PH

Lentinus edodes is one of the cultivated species among edible fungi in China,and its production has been the first among various edible fungi for a long time.In recent years,there have been more and more factories producing shiitake mushroom bags,but the factory-produced mushroom bags often have the problem of abnormal germination,mainly manifested by the slow growth of mycelium,or even no germination,but the specific reason is not clear.During the investigation,it was found that during the large-scale open storage of wood chips,the pH of the wood chips was reduced by fermentation.The factory often used lime or calcium carbonate to adjust the culture material to pH 6-7,but still inhibited the growth of mushroom mycelium.To resolve this issue,this paper clarified the mechanism by which pH affects the growth of mycelia by studying the relationship between ambient pH and the growth and metabolism of L.edodes mycelia.The research results of this paper are as follows:1.Ambient pH affects mycelial growth of L.edodes.The high concentration of citric acid and lactic acid can inhibit growth of L.edodes mycelium in the acidified sawdust.Without buffering,the mycelium can grow at pH 3-7 on the PDA medium;when buffered,the mycelium can only grow at pH 3-4.The calcium citrate and calcium lactate formed after adding lime have a buffering effect,which significantly inhibits growth of L.edodes mycelium.The effect of buffering becomes more obvious as the concentration of organic acids increases.When the pH is adjusted to 4,the mycelium grows optimally and eliminates the effects of buffering capability and organic acids.2.L.edodes secretes oxalic acid to lower ambient pH.Growing in an environment where ambient pH is higher than 4,the hyphae will gradually reduce ambient pH to 3-4.The amount of oxalic acid secretion increases with the increase of ambient pH and growth rate also decreases with increasing pH.The pH of the medium will increase when calcium carbonate is added exogenously,and a transparent zone composed of calcium oxalate crystals will form on the calcium carbonate medium.L.edodes mycelium has low tolerance to soluble oxalate(lower to 2.5 mM),but has high tolerance to insoluble calcium oxalate and the concentration can reach to 50 mM.3.Transcriptome analysis of the metabolic pathway of oxalic acid in L.edodes.Four kinds of L.edodes mycelium grown under different pH conditions were selected for transcriptome analysis.There were found 9073 differential genes.In differential gene analysis,it was found that different pH may affect the changes of polysaccharide,trehalose,and glycogen content in L.edodes mycelium,and determined the important relationship between the oxalic acid metabolism pathway and the citric acid cycle and glyoxylic acid cycle.Gene cloning and prokaryotic expression of LeOAH1,a key gene for oxalic acid synthesis,found that the main factor regulating LeOAH1 gene expression is the transcription factor PacC in response to pH..In summary,by studying the relationship between pH and the growth of L.edodes,this article reveals the oxalic acid metabolism pathway of L.edodes,and clarifies the important influence of pH on the growth of L.edodes mycelium,which provides theoretical guidance for the production of L.edodes.