## 6 Industrial Production of _C. militaris_  
### Overview of Production Methods  
The production of _C. militaris_ involves several key stages, each requiring specific equipment to ensure efficiency and quality. The primary methods of cultivation are solid-state fermentation (SSF), liquid fermentation (submerged culture), and hybrid systems. In SSF, grain substrates like rice or wheat bran are used, necessitating equipment for substrate preparation such as mixers, steamers for sterilization, and incubation chambers to maintain controlled environmental conditions [86]. This method simulates the natural growth conditions of the fungus and is favored for its simplicity and low capital requirement. Conversely, liquid fermentation requires bioreactors that provide precise control over parameters like temperature, pH, and oxygen levels [87]. These systems are automated with sensors and pumps to manage the addition of nutrients and maintain optimal growth conditions. Hybrid systems combine these methods, starting with liquid culture to rapidly expand biomass before transferring to solid substrates to boost secondary metabolite production, necessitating equipment for both methods (Figure 4).  
The choice of production method significantly influences the potential output and associated costs. SSF is typically less expensive to set up but may offer lower yields compared to liquid systems. Average yields for SSF can range from 0.1 to 0.5 g of dry  
Figure 4: Overview of production systems for _C. militaris_.  
weight per liter of substrate, depending on the strain and substrate composition. The cost of establishing an SSF setup can vary but generally remains low, focusing mainly on the cost of substrates and simple fermentation setups [87]. Liquid fermentation, while more costly in terms of initial setup due to the need for sophisticated fermenters and control systems, allows for higher biomass production. Yields from liquid fermentation can reach 10 to 20 g/L, with operational costs driven by nutrient media and energy consumption for maintaining fermentation conditions. The capital investment for a moderate-sized liquid fermentation facility can range from USD 100,000 to 500,000, with operational costs varying based on the scale and efficiency of the processes.  
Hybrid systems aim to maximize the benefits of both SSF and liquid fermentation, facilitating an initial liquid culture phase followed by a transfer to solid-state conditions. This method can enhance the yield of specific bioactive compounds by 10-15% compared to individual methods. The setup cost for hybrid systems is significant, often exceeding the sum of individual setups, but they offer flexibility in production based on demand for different compounds. Operational costs for hybrid systems are higher due to the complexity and the need for additional steps in transferring cultures and maintaining two types of fermentation environments. Economic viability across these methods depends not only on the production outputs and costs but also on the market value of the compounds produced. Cordycepin, for instance, has a high market value that can offset the higher costs of production in liquid or hybrid systems. The profitability of each method thus depends on balancing the higher yield and quality of bioactive compounds against the increased investment and operational costs.  
Continuous advancements in biotechnological tools and optimization of fermentation parameters are critical for reducing costs and enhancing yields. Genetic engineering, for example, offers prospects for strain improvement that could significantly boost production efficiency [88]. Moreover, ongoing research into cheaper substrate alternatives and energy-efficient fermentation processes could further enhance the economic viability of cultivating _C. militaris_ commercially. As market demand for natural health products continues to grow, optimizing production methods to maximize yields while minimizing costs will be crucial for maintaining competitiveness in the biotechnology sector.