Factors affecting the cesium transfer factor to shiitake (Lentinula edodes) cultivated in sawdust medium

The transfer factor (TF) of radioactive cesium-137 (137Cs) to shiitake (Lentinula edodes) cultivated on bed logs varies greatly. Therefore, the present study investigated which factors affect the TF using stable cesium-133 (133Cs) and sawdust medium with 5% rice bran as a model, which had similar 133Cs TFs to bed-log cultivation. It was found that the Cs concentration and nutrient concentration (represented by the nitrogen concentration) concerned with the TF in the model sawdust medium. In addition, the TFs calculated using total 137Cs and 133Cs concentrations differed in both bed-log cultivation and the model sawdust medium cultivation, while the TFs calculated using exchangeable 137Cs and 133Cs concentrations were the same in sawdust medium cultivation, indicating that exchangeable Cs in the medium is the source of Cs for the fruiting body and the former difference was due to the presence of other chemical speciation of Cs that could not be absorbed. One purpose of the TF on the mushroom farm is to determine the fruiting body 137Cs concentration at the start of bed-log cultivation, therefore the prediction method of TF are discussed considering the future changes of 137Cs concentrations in trees.

TECHNOLOGY OF MUSHROOM CULTIVATION

Mushroom cultivation has been developed by two ways, i. e., one based on cultivation by wood-log and another based on cultivation by non-wood-log. Non-wood-log cultivation would be categorized into two aspects. Mushroom cultivation under non-aseptic condition, i. e., one characterized by the processes of fermentation (composting) and casing, and another characterized by using sterilized media followed by cultivation process associated with strict control of environmental factors such as light, temperature, humidity, and CO2 concentration.