Solid-state fermentation in rotating drum bioreactors: operating variables affect performance through their effects...

Area of Science:

• Biotechnology
• Microbial Engineering
• Bioprocess Engineering

Background:

• Solid-state fermentation (SSF) is a key bioprocess utilizing microbial growth on solid substrates.
• Optimizing SSF bioreactor operation is crucial for efficient industrial applications.
• Understanding the interplay between operational parameters and substrate properties is essential for process control.

Purpose of the Study:

• To investigate the impact of bioreactor operational variables on fungal growth during SSF.
• To elucidate the role of transport phenomena (mixing, shear, heat, and mass transfer) in SSF performance.
• To determine how substrate characteristics influence the effectiveness of transport processes in SSF.

Main Methods:

• Cultivation of Aspergillus oryzae ACM 4996 in 18.7 L rotating drum bioreactors.
• Comparison of fungal growth on an artificial gel-based substrate versus steamed wheat bran.
• Evaluation of different operational conditions, including rotational speed and agitation (static vs. agitated).

Main Results:

• On gel substrate, increased rotational speed led to decreased fungal growth, likely due to shear stress.
• On wheat bran, agitated conditions promoted fungal growth over static conditions, indicating improved heat and mass transfer.
• Transport phenomena and substrate properties were identified as critical factors influencing SSF performance.

Conclusions:

• Bioreactor operational variables significantly impact SSF performance by altering transport phenomena.
• Substrate characteristics dictate the necessity and rates of transport processes, influencing which phenomena become rate-limiting.
• This study enhances the understanding of bioreactor operation effects on SSF, paving the way for optimized bioprocesses.