Influence of the aeration rate on the yields of the biocontrol nematode Heterorhabditis megidis in monoxenic liquid cultures

The entomopathogenic nematode-bacterium complex Heterorhabditis megidis - P hotorhabdus luminescens was cultured in 10-1 internal loop bioreactors with marine impellers at aeration rates of 0.3 vvm and 0.7 vvm. Process paramet ers like impeller velocity and oxygen saturation were controlled at equal s et points. The bacterial density was assessed at 24 h. Nematode dauer juven iles (DJ) were then inoculated and the development to adults after 8 days a nd final DJ yields after 16 days were recorded. The bacterial population de nsity and the nematode inoculum development was variable and was not influe nced by the aeration rate. A significant effect on the yield was recorded a t the highest aeration rate. This result was confirmed by a direct comparis on in two 5-1 internal loop glass bioreactors at 0.3 vvm and 1.0 vvm, which were inoculated with nematode and bacterium pre-cultures from the same fla sk culture. Possible reasons for the positive correlation between aeration rate and DJ yield are discussed.