Enhancing β-mannanase production by controlling fungal morphology in the bioreactor with microparticle addition

•Evaluation of talcum and Al2O3 as microparticle was succesfully studied in a 2-L bioreactor.•The highest β-mannanase activity was 744.35U/ml for 5g/L of Al2O3 in glucose-based medium.•The highest β-mannanase activity for recombinant A. sojae was achieved in bioreactor trials. Beta (β)-mannanase is an industrial enzyme that has a wide range of uses in industry. Chemically, β-mannanase mainly influences the β-1,4-mannose linkages of galactomannans. Many microbes, particularly Aspergillus species, can be utilized to produce mannanases. On the other hand, excessive filamentous clumps of Aspergillus species in bioreactors are difficult to control. Therefore, this study sought to limit the clumps resulted from the excessive fungal growth by adding microparticles into the fermentation medium. Fed-batch fermentations were performed with and without microparticles (control). As a microparticle agent, aluminum oxide (Al2O3) and talc (Mg3Si4O10(OH)2)) were evaluated as to their effect on fermentation performance. The highest β-mannanase activities were 744.35 and 356.79 U/mL for 5 g/L of Al2O3 and talc, which were 14.16- and 6.80-fold greater, respectively than in the control fermentation. Most of the treatments improved the performance of the fermentation process as the microparticles appeared to disturb the initial phase of spore aggregation. The most effective microparticle type and concentration for production of β-mannanase in a stirred tank bioreactor with a glucose-based medium were determined to be 5 g/L of Al2O3. These results indicate that the use of microparticles improve β-mannanase fermentation conditions by controlling excessive fungal growth.