Production of Fungal Phytase in an Innovative Trickle Bed Bioreactor

Abstract

Excessive temperature rise and drying of substrates are two common problems in solid state fermentation. In order to overcome these problems, an innovative trickle bed bioreactor (TBBR) was designed and tested for the production of fungal phytase by the cultivation of Aspergillus ficuum on wheat straw. In this reactor, a helical perforated bed acts as a support for the substrate. Rotation of this bed in a baffled column produces gentle mixing and separates agglomerated substrates. Intermittent water trickling during fermentation removes product and heat from the fermentation medium partially. For phytase production in the TBBR, the bioreactor was filled with moistened sterilized wheat straw, inoculated with the spores of the fungus. After 3 days, water was trickled on the substrate for 1 min every 24 h. The enzyme in the trickling liquid, and the extracted enzyme from the residual straw after fermentation, were quantified. An equal size traditional packed bed bioreactor (PBBR) was also operated as a control. Phytase production in this TBBR was 54.95% higher than the PBBR. Monitoring the temperature in both bioreactors, moreover, showed lower temperature increase in the TBBR compared to the PBBR.