Development of a low-cost sterilization biological indicator using Bacillus atrophaeus by solid-state fermentation.

Area of Science:

• Microbiology
• Biotechnology
• Process Engineering

Background:

• Biological indicators (BIs) traditionally require complex, multi-step downstream processing for bacterial sporulation.
• Cost-effective and streamlined production methods for BIs are needed to improve accessibility and efficiency.

Purpose of the Study:

• To evaluate the use of fermented material as the final product in BIs, minimizing processing steps and costs.
• To assess inexpensive inert supports for Bacillus atrophaeus solid-state fermentation (SSF) and their suitability for direct use in BI production.

Main Methods:

• Solid-state fermentation (SSF) of Bacillus atrophaeus on vermiculite, sand, and sugarcane bagasse.
• Assessment of spore production (CFU/g) and direct utilization of fermented material.
• Evaluation of sterilization resistance (dry heat, ethylene oxide) and cost-effectiveness.

Main Results:

• All supports yielded high spore counts (10^7–10^9 CFU/g).
• Sand demonstrated superior performance as an inert support due to excellent homogenization, filling properties, and recovery medium compatibility, facilitating direct use of fermented product.
• The dried fermented product exhibited significant resistance to sterilization, with D-values of 6.6 min for dry heat (160°C) and 6.5 min for ethylene oxide (650 mg/L).
• This novel process achieved a minimum cost reduction of 48%.

Conclusions:

• Sand is a highly effective and economical inert support for Bacillus atrophaeus SSF in biological indicator production.
• Utilizing fermented material directly as the final BI product significantly reduces processing steps and costs.
• This approach offers a novel, cost-effective method for producing robust biological indicators.