| Because of its unique medicinal value and food taste delicious,was edible and widely cultivated all over the world.Recent years,cadmium pollution in the lentinula edodes is reported gradually,food safety has once again aroused widespread attention.Based on extensive investigation of heavy metals in the main producing mushroom areas,we illuminated current condition of heavy metal pollution on mushroom.Explored the effective prevention and control technology for L.edodes fruiting bodies via the study of Cadmium enrichment rule on L.edodes.According to the relevant standard in "NYT749-2012 Green food Edible fungi " this study aimed at the statistical analysis of As,Hg,Cd and Pb content in fruiting bodies from main producing areas in Henan,revealing that over-limit ratios of heavy metals were As>Cd>hg>Pb.Hg and Cd contents of mushroom in Biyang exceeded the standard,and over-limit ratios were 6.7%and 33%,respectively.The arsenic content of mushroom in Sanmenxia was high,while all heavy metal contents of Xixia mushroom were low,which may be related to environmental conditions,planting materials and planting modes in all regions.In this part,we aimed at the analysis of Cd source based on the fact that heavy metal Cd pollution was a common problem in L.edodes.The results suggested that there was a significant positive correlation in the Cd concentration of shiitake fruiting bodies and the sawdust of the substrates,but there was no obvious correlation to it of bran and gypsum.Highly significant differences were generated in Cd concentration from different region sawdust.However,the Cd concentrations from different region bran and gypsum were consistent.The Cd concentration of shiitake picked later period was lower than that of mushroom harvested in the initial stage,and yet there was no significant correlation among different harvest stages.Correlation analysis demonstrated that the adsorption function of the cap was y1=-7.716x2+23.821x-1.868,R2=0.998;the adsorption function of the stipe was y2=-5.928x2+15.105x-1.568,R2=0.999.The Cd concentration of mushroom(y1)was lower than the safe concentration threshold that was 1.5 mg/kg.when the compost Cd concentration(x)was lower than 0.1485 mg/kg and the sawdust Cd concentration was below 0.1188 mg/kg that was treated as the upper value of the sawdust Cd concentration for controlling shiitake Cd pollution via experiment veritification.The Cd accumulation rule of L.edodes mycelia displayed that the trend of mycelial growth rate was gradually decreasing with the increase of exogenous Cd concentration;SOD,CAT and POD activity of L.edodes mycelia were increasing at first and then decreasing;the roles of three enzymes in different periods were different as mycelial growth time change,and Cd transferred gradually from cell wall to cytoplasm.Under the help of microscope,we found that the detoxification mechanism when cell encountered to heavy metal Cd pollution maybe isolating Cd to the vacuole.At the same cultivation condition,the accumulation capacities of strains 607 and 908 were weaker.The cationic interference ability on heavy metal cadmium were Mg2+>Ca2+>K＋.Therefore,during prevention and control of heavy metal cadmium in L.edodes fruiting bodies,adding exogenous magnesium sulfate(50mg/kg in dry weight)and 2.5%cadmium on the basis of conventional substrates could decrease the cadmium content in mushroom cap to 49%and 54%,respectively,which could generate good guidance for L.edodes production safety. |
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