Variable pressure pulsation frequency optimization in gas double-dynamic solid-state fermentation (GDSSF) based on heat balance model

• Heat balance model involving pressure pulsation frequency was proposed in GDSSF.
• Heat transfer was enhanced and cellulase activity increased under variable frequency.
• Variable frequency was the preferred operation mode than the constant one.
• An efficient and practical method for frequency optimization was established.

Heat accumulation is considered as the main limitation of microbial growth in solid-state fermentation (SSF). Gas double-dynamic solid-state fermentation (GDSSF) has been devised based on our years of research to strengthen heat transfer by periodic air pressure pulsation and cycle flow. The pressure pulsation frequency is a key parameter which determines heat removal efficiency. In this work, heat balance model integrating pressure pulsation frequency, microbial metabolism, evaporative cooling and heat exchange with air was established. Pressure pulsation frequency was then optimized based on the heat balance model. Results indicated that the optimal pressure pulsation frequency was variable at different fermentation stages, under which the medium temperature increase extent reduced from 4.2 °C to 2.5 °C while the fermentation production (cellulase activity) increased by 9.23% than that under the conventional constant frequency. Therefore, the variable frequency was the preferred operation mode than the conventional constant one in GDSSF. The optimization method established in the present study has been proved effective and practical.

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