PILOT-SCALE LIQUID CULTURE AND HARVESTING OF AN ENTOMOPATHOGENIC NEMATODE, HETERORHABDITIS-BACTERIOPHORA

A population of the insect parasitic nematode Heterorhabditis bacterio phora was successfully cultured on two complex liquid media at both 20 - and 500-liter scale in bubble column fermenters. Yields of greater t han or equal to 10(5) infective juveniles (IJ) ml(-1) were achieved. O n 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 medi um 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 wer e 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 juvenil e nematodes from the 500-liter fermenter were then successfully separa ted from their liquid medium using both a basket centrifuge and a scro ll decanter centrifuge. Infective juvenile nematode concentrations bet ween 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 bio logical 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.