| Lentinula edodes is one of the widely cultivated mushroom in our country,and its yearly output ranks the first in all the mushrooms for a long time.In recent years,with the increasing exports of L.edodes,the problem of excessive heavy metals has been concerned by the public.Arsenic is a toxic heavy metal element,its exceeding in the L.edodes happens occasinally.In this study,we have learnd about the current arsenic contaminating status through the sample investigation of cultivation material and fruiting body from L.edodes production regions,did research on the impact of exogenous additives(arsenate,phosphate,silicate)and temperature on the absorption of arsenic in mycelium and friuting bodies,and compared the differences of arsenic content in different strains of L.edodes and different portions of fruiting body,then discussed the arsenic accumulation regulation and its contamination prevention technology.The survey of arsenic contamination in L.edodes production regions of Hubei and Henan province indicates that the arsenic contamination rarely happens.Accroding to the relevant standard in “GB 2762-2012 China National Food Safety Standard: Maximum Limit of Contaminants in Food”,only one sample from Shahedian is out of limits,whose arsenic content is about 0.667 mg/kg.Study on the effects of exogenous additives on absorption of arsenic in mycelium shows that the higher concentration of arsenic in the culture medium,the stronger inhibition of mycelium growth,and it almost cann't grow when arsenic concentration up to 2 mg/L.Nevertheless,the arsenic content in mycelia is getting higher with the arsenic concentration increased.When added certain concentrations of phosphate into the medium,the growth speed of mycelium in medium with As(V)is significantly higher than the control group with no any phosphate added.But for mycelium in the medium added As(?),the phosphate dosen't have any significant effects.It suggests that PO43-could mitigate the inhibitory effect of As(V)on hypha growth.Then the influence of temperature on the arsenic content in mycelium was studied.The result reveals that the mycelia grown in lower temperature(16°C-22°C)can absorb more arsenic then in higher temperature(25°C-28°C).After adding different arsenic concentrations into the cultivation materials,the results of cultivated experiments show that arsenic content in fruiting bodies gets increased,when added more exogenous arsenic in substrates.And the linear regression analysis indicates,that there is a significant positive correlation between the arsenic contents of substrates and fruiting bodies,and they conform to the regression equation,y = 0.5458 x + 0.1254,R2=0.9935.When a certain concentration of arsenic is added to the substrate,the arsenic content in fruiting bodies of different varieties of L.edodes is different.In the five test strains,the fruiting bodies of Aihua1 have the highest arsenic content,while the Aihua2 have the lowest,and the difference is significant.The fruiting bodies from different harvests also have the different arsenic content.The first harvest of fruiting bodies have the apparently higher arsenic content than the second.Arsenic content in different portion of the fruiting body is also different,the gill has the highest content,then the cap,the stipe has the lowest.In conclusion,arsenic contamination of the L.edodes is sporadic.The arsenic content of the fruiting bodies increases with the increase of arsenic concentration in the substance.Temperature can slightly affect the amount of the mycelium's absorption of arsenic.When added certain concentrations of phosphate to the medium,it can significantly mitigate the inhibitory effect of As(V)on the mycelium growth,but cannot affect the inhibiting of As(?).Selecting appropriate strains of L.edodes can help control the arsenic content in fruiting bodies. |
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