Optimization of mycelial culture conditions of the entomopathogenic fungus Cordyceps blackwelliae in submerged culture

Cordyceps blackwelliae is an entomopathogenic fungus described over recent years and is easy to grow fruiting bodies. Nutritional requirements and cultivation conditions for optimal mycelial growth of the fungus remain unclear. Herein, we optimized the mycelial growth conditions of the fungus in submerged culture and investigated the relationship between mycelial growth and mitochondrial DNA (mtDNA) copy numbers within cells. The highest mycelial weight was observed at a temperature of 25 degrees C and a starting pH of 6 in the liquid media. Through comparative analyses of 12 carbon sources, nine nitrogen sources, five C to N ratios, and four macro-elements, it was determined that optimal mycelial growth occurred in the presence of sucrose, yeast extract, the C to N ratio of 18:1, and K+. No significant differences were observed when comparing four trace elements or among six vitamins. Further optimization of sucrose and yeast extract concentrations, along with cultivation temperature, was conducted using response surface interaction analysis, leading to the identification of optimal conditions at 20.42 g/L sucrose, 4.71 g/L yeast extract, and 26.2 degrees C. Under these conditions, mycelial dry weight reached 11.257 g/L after 6 days of cultivation. Quantitative PCR analyses and high-throughput DNA sequencing revealed a positive correlation between mycelial growth and mtDNA copy numbers within the cells. The findings of this study are expected to enhance the large-scale production of the fungus.