Performance of a fixed-bed solid-state fermentation bioreactor with forced aeration for the production of hydrolases by Aspergillus awamori

• Amylases, cellulases, xylanases and proteases were produced by solid-state fermentation (SSF).
• A fixed-bed bioreactor with forced aeration was efficiently used for enzyme production.
• Despite temperature gradients, significant enzyme activities were obtained.

In order to overcome scale-up limitations of conventional tray-type solid-state fermentation (SSF) bioreactors, a cylindrical fixed-bed bioreactor with forced aeration was investigated for the production of a pool of industrially relevant enzymes by Aspergillus awamori IOC-3914 using babassu cake as raw material. Significant internal radial and axial temperature gradients were observed (up to 2.4 °C cm−1), but despite of this, good titers of the production of the six enzyme groups evaluated was observed in all three bed layers sampled. Maximum activities of exoamylases, endoamylases, proteases, xylanases and cellulases (CMCase) were, respectively, 73.4, 55.7, 31.8, 23.8 and 6.2 U g−1. Moreover, a considerable production of isoamylases (27.0 U g−1) was observed, although the production of starch-debranching enzymes by SSF is rarely reported. Productivities were highest for endoamylases (0.95 U g−1 h−1) and exoamylases (0.67 U g−1 h−1). The present results show that despite considerable axial and radial temperature gradients, significant levels of different enzymes can be obtained, giving evidence that fixed-bed bioreactors with forced aeration present a promising alternative in terms of instrumented bioreactors for SSF processes.