Mass production of the entomopathogenic nematode, Steinernema carpocapsae CABA01, through the submerged monoxenic culture in two internal-loop airlift bioreactors with some geometric differences

The submerged monoxenic culture of the entomopathogenic nematode, Steinernema carpocapsae CABA01, was carried out in two internal-loop airlift reactors (R1 and R2) with some geometric differences. Two runs each reactor were carried out at operating conditions V-L = 4.22 L, Q = 1-1.5 vvm, T = 22 degrees C. The culture broth apparent viscosity changed from 2 to 12 mPa s determining global changes in both hydrodynamics (expressed as the dimensionless Reynolds number, Re) and oxygen transfer conditions (expressed as the k(L)a coefficient). Such changes were 170 < Re < 3080: 1.9 < k(L)a (10(-2) s(-1)) < 3.5 for R1 experiments, and 400 < Re < 10.060; 1.9 < k(L)a (10(-2) s(-1)) < 3.5, for R2 experiments. Infective juvenile stage (IJ) concentrations of 250,000/mL were achieved in R2 experiments whereas notably lower ones were obtained in R1 experiments (110,000 IJ/mL, approximately). The hydrodynamic conditions in both riser and downcomer sections of R2 experiments involved higher inertial forces than the corresponding ones to R1 runs, implying values of (Re-R2/Re-R1)(riser) from 2.3 to 3.3 and (Re-R2/Re-R1)(downcomer) from 1.8 to 2.5. These results suggest that higher inertial forces would promote the mating process among the vigorous adult nematodes of the first generation, probably due to encourage female-male encounters in response to a better mixing of the culture broth. Further, the nematode reproduction appeared to be greatly influenced by the reactor geometry. (C) 2011 Elsevier B.V. All rights reserved.