Adding talc microparticles toAspergillus terreusATCC20542 preculture decreases fungal pellet size and improves lovastatin production

Abstract

Changing fungal morphology with the use of morphological engineering techniques leads to improving the production of metabolites by filamentous fungi in the submerged culture. Adding mineral microparticles is one such simple method to change fungal pellet size. Here, it was studied for a lovastatin producer,Aspergillus terreusATCC20542. The experiments were conducted in shake flasks and 10 μm talc microparticles were added to the preculture. Intrapellet oxygen concentration profiles were determined by an oxygen microprobe. Talc microparticles caused a decrease ofA. terreuspellets diameter from about 2000 to 900 μm, dependent on their concentration in the preculture. Smaller pellets produced more lovastatin, whose titre exceeded then 120 mg L−1, utilising more lactose. The decrease in pellet size resulted in changes of oxygen concentration profiles in the pellets. The estimated critical pellet diameter, at which the non‐oxygenated zone was observed in the centre of the pellets, was 1700 μm. Smaller pellets were fully penetrated by oxygen. To conclude, facilitated diffusion of oxygen into the pellets of smaller diameter and their less dense structure made lactose utilisation byA. terreusmore efficient, which ultimately increased lovastatin production in the runs with talc microparticles added, compared to the control runs.