Mushroom Spawn Production Technology（2）

In mushroom spawn production, sterilization is the foundation of success. Whether you’re preparing grain spawn, mother cultures, or liquid media, eliminating contaminants is crucial. The most effective and widely adopted method in professional mushroom production is high-pressure steam sterilization—performed using a specialized autoclave designed for edible fungi.

Why Sterilization Matters in Spawn Production

Contaminants like bacteria, molds, and wild fungi can quickly ruin a batch of spawn. Even microscopic traces can outcompete mushroom mycelium. Sterilization ensures that only your intended fungal species colonizes the substrate or culture medium, creating clean, vigorous spawn ready for further expansion or inoculation.

High-Pressure Sterilization Units for Edible Fungi

How They Work

A professional high-pressure autoclave for mushroom spawn production operates as a sealed, pressure-resistant chamber—often with a double-layer (jacketed) structure. Water is heated within the inner chamber or outer jacket to generate steam. As the steam builds up in a sealed environment, it can exceed 100°C, reaching temperatures of 121°C or higher at elevated pressure.

This high-temperature steam penetrates deeply into the culture vessels or substrate bags, destroying:

1、Microbial vegetative cells

2、Heat-resistant spores

3、Fungal competitors

A properly operated autoclave can achieve complete sterilization in a short time, often 60–120 minutes depending on the load and materials.

Key Features to Look For

1、Pressure and Temperature Control
Precise settings help tailor sterilization cycles for different substrates (e.g., grain vs. liquid).

2、Air Exhaust System
It’s vital to remove cold air from the chamber before pressurization; trapped air can reduce sterilization effectiveness.

3、Capacity Options
Available in small units (for labs or small-scale use) and large horizontal chambers (for spawn factories).

4、Safety Valves and Interlocks
These ensure safe operation at high temperatures and pressures.

Comparison to Other Sterilization Methods

High-pressure steam sterilization is superior to hot water boiling or chemical sterilization in terms of reliability and depth of penetration. While those alternatives might work for low-risk substrates, only autoclaving ensures a truly sterile environment—critical for spawn production.

Tips for Effective Sterilization

• Always allow steam to purge air from the chamber fully before starting the holding time.

• Avoid overloading the autoclave; steam must circulate freely.

• Check and maintain seals, pressure gauges, and exhaust valves regularly.

In the next article, we’ll examine how to maintain sterility during inoculation, comparing two key tools: the inoculation box and the laminar flow hood.