From shake flasks to stirred fermentors: Scale-up of an extractive fermentation process for 6-pentyl-α-pyrone production by Trichoderma harzianum using volumetric power input

An extractive fermentation process for 6-pentyl-α-pyrone (6PP) production by Trichoderma harzianum was scaled-up from 500 ml shake flasks to 10 l stirred tank bioreactors keeping constant the volumetric power drawn (P/V). Two general effects of P/V over 6PP production were observed: at the low P/V cultures (from 0.08 to 0.4 kW/m3) a gradual increase in P/V improved 6PP production; meanwhile, at P/V values above 0.6 kW/m3, 6PP concentration was significantly reduced due to higher hydrodynamic stress. Overall, maximum 6PP production (230 mg/l) was a function of P/V, regardless of the cultivation scale. However, agitation with impellers triggered an earlier synthesis of 6PP in the 10 l bioreactor cultures, if compared to their shake flask counterparts. This suggests a physiological mechanism through which this fungus responds to hydrodynamically stressful conditions.