Pilot-scale liquid culture and harvesting of an Entomopathogenic nematode, Heterorhabditis bacteriophora

A population of the insect parasitic nematode Heterorhabditis bacteriophora was successfully cultured on two complex liquid media at both 20- and 500-liter scale in bubble column fermenters. Yields of greater than or equal to 10(5) infective juveniles (IJ) ml(-1) were achieved. On medium 1 for the two 20-liter cultures, culture times were 15 and 20 days, respectively, at 20 degrees C to reach 10(5) IJ ml(-1). On medium 2 it took 30 and 45 days, respectively, to reach 10(5) IJ ml(-1) in the 20-liter fermenter and the 500-liter fermenter. Culture times were acceptable on medium 1 but its cost (U.S.$3 liter(-1)) was threefold greater than that of medium 2 (U.S.$0.9 liter(-1)). Infective juvenile nematodes from the 500-liter fermenter were then successfully separated from their liquid medium using both a basket centrifuge and a scroll decanter centrifuge. Infective juvenile nematode concentrations between 8 and 19 times those of the feed stream were achieved. Some loss of viability occurred during the scroll decanter separation. The scale-up methodology is thus set for possible commercialization of this biological control agent, but further work on medium design, formulation, and efficacy testing in the field is required before proceeding along this course. (C) 1996 Academic Press, Inc.