Cultivation and Harvesting of Selenium-Enriched Ganoderma lingzhi and Spent Medium Using Kudzu Vine as Substrate

In order to harvest selenium-enriched fruiting body and spores of Ganoderma lingzhi and spent medium, G. lingzhi was cultivated in kudzu vine as substrate and the bio-transformation of selenite was evaluated. The growth medium consisted of Kudzu vine supplemented with 20% wheat bran or sawdust or none. The growth medium was supplemented with 0, 10, 20, 30, and 50 mg/kg of sodium selenite. We found a significant difference in spawn run speed, fruiting body and spore yields when Kudzu vine was supplemented with wheat bran or sawdust. However, when whole-kudzu vine was used alone as substrate, it resulted in a significantly lower spawn run speed, fruiting body, and spore yields compared with kudzu vine + sawdust substrate and kudzu vine + wheat bran substrate. The selenium content in fruiting body and spores increased with increasing sodium selenite supplementation and approximately equaled half of the selenium in the substrate. No selenite was detected in both the fruiting body and spores. However, in the spent medium when sodium selenite was supplemented at 10, 20, 30, 50 mg/kg, the residual selenite concentration decreased to 0.45, 0.72, 1.29, and 1.95 mg/kg, respectively, suggesting a higher selenite transformation (92.27–93.57%). In conclusion, if Ganoderma fruiting body and spores were to be harvested for human consumption, approximately 50 mg/kg selenite should be added to the growth substrate. On the other hand, if the spent medium was to be used as an organic selenium source, the optimal sodium selenite supplementation level would be 10 mg/kg.