Potential Use of Polyethylene Glycol in the Mass Production of Nonsynnematous and Synnematous Strains of Hirsutella thompsonii Fisher in Submerged Culture

Polyethylene glycol (PEG 6000) at six different concentrations (1, 2, 3, 4, 5 and 6% w/v) in Sabouraud dextrose broth influenced both quality and quantity of the biomass of Hirsutella thompsonti (nonsynnematous) and H. thompsonti var. synnematosa (synnematous) in submerged culture. Whereas the number of colony-forming units (CFU), wet and dry weights of both nonsynnematous and synnematous strains increased, pellet number and size decreased with the increasing concentration of PEG in the medium. However, there was no significant effect of the chemical on conidial germination, although conidiation of biomass of both strains was slightly delayed. The intended aim of getting more of hyphal fragments and less of mycelial pellets with the chemical was achieved as reflected in the maximum CFU obtained with 6 per cent PEG in H. thompsonii (360.53 × 10³/ml) and H. thompsonti var. synnematosa (237 × 10³/ml). Compared with the respective controls, the highest level of PEG produced 6 and 2.8 times less number of fully-formed pellets in the nonsynnematous and synnematous strains, respectively.