Camptotheca acuminata Decne residue after camptothecin extract as a substrate to produce mushroom spawn

Abstract

Currently in China, no technically and economically viable methods exist to handle large quantities of Camptotheca acuminata Decne residue (CA residue) after camptothecin extract while there is a great demand for low cost alternatives to replace the cottonseed hull-based materials used in commercial mushroom culture. Hence, it is of importance for camptothecin extract factories and mushroom producers to explore the utilization of CA residue in mushroom industry. We conducted a research to study how partially or completely substituting traditional mushroom substrate by CA residue would influence the mycelial growth in mushroom spawn production. 5 mushroom strains from 4 species were used in the test, i.e., oyster mushroom (Pleurotus ostreatu) strains, Zayou No. 1 and Xide 33, needle mushroom (Flammulina velutipes) strain ChuanjinNo. 3, hairy wood ear (Auricularia polytricha) strain Huang Er No. 10, and shiitake (Lentinula edodes) strain Wuxiang. The nutrient element composition and heavy metal contents of CA residue were determined to ensure its safety and to determine its appropriate component in the substrate formulation for mushroom spawn production. The four substrate formulations (one control — CK, and three treatments, named, T1, T2, T3,) contained 0%, 40%, 79%, and 100% CA residue, respectively, to allow comparison of the fungal mycelial growth. The control (CK) was the popularly used formulation in Chinese commercial mushroom production, comprising of 73% cottonseed hulls, 10% sawdust, 15% wheat bran, 1% lime, 1% white sugar (percentage by weight). All mushroom spawns of the five strains in the four treatments were incubated under the same conditions. The results showed that mycelia of the five mushroom strains grew significantly faster on the substrates containing CA residue than on the substrate with no CA residue (CK). There were no significant differences in the mycelial growth rate among treatments containing CA residue for the two oyster mushrooms and the needle mushroom, but mycelial growth rate in treatments T2 and T3 was significantly higher than in treatment T1 for hairy wood ear and shiitake. The results suggest that CA residue can be used to culture oyster mushroom, needle mushroom, hairy wood ear, and shiitake spawn, and the medium containing CA residue can stimulate their mycelial growth. The commercial production of mushroom spawn using CA residue not only brings better economical benefits including lower cost to mushroom producers, but also reduces environmental pollution by providing a means to reduce dumping and piling of CA residue.