Production of 6-pentyl-α-pyrone by Trichoderma harzianum cultured in unbaffled and baffled shake flasks

When Trichoderma harzianum was cultured in unbaffled shake flasks, increased agitation (100-300 rpm) resulted in higher biomass production and higher titers of 6-pentyl-alpha-pyrone (up to 100 mg/l). The fungus grew as loose aggregates, being smaller at the highest agitation rate. In baffled flasks, loose aggregates were only observed at the lowest agitation speed (100 rpm). At higher speeds, nearly 90% of the total biomass was attached on the surface of the flask' wall. The remaining biomass (suspended in the liquid) was in the form of macroscopic pellets. 6-Pentyl-alpha-pyrone (6-PP) titer in baffled flasks cultures was maximum (96 mg/l) at 100 rpm and decreased at higher agitation rates. The data suggest that specific 6-PP productivity was determined by hydrodynamic stress, reaching a maximum for an estimated volumetric power drawn of about 0.9 kW/m(3) and then dropping at higher volumetric power drawn. (C) 2003 Elsevier Science B.V. All rights reserved.