Lab-scale in vitro Mass Production of the Entomopathogenic Nematode Heterorhabditis bacteriophora Using Liquid Culture Fermentation Technology

Abstract

The objective of this research is to develop fermentation methodology for the production of the biocontrol agent Heterorhabditis bacteriophora. Deployment of this organism will reduce the use of chemical insecticides which threaten the environment. This study shows how to produce the entomopathogenic nematode (EPN) Heterorhabditis bacteriophora and its bacterial symbiont Photorhabdus luminescens utilizing an in vitro, monoxenic liquid culture. EPNs were cultured in three different bioreactor working volumes of 1.5, 4 and 7 liters with initial nematode inoculation concentrations of approximately 2x103/mL. Liquid nematode media was conditioned with the bacterial symbiont 24 hours prior to nematode inoculation. Within three days after inoculation, infective juveniles (IJs) developed into self-fertilizing hermaphrodites and eventually produced IJ offspring. Maximum nematode densities were obtained seven days post-nematode inoculation. All three working volumes (1.5, 4 and 7 liters) produced final yields of 4.6x104 ± 2000 IJs/mL, 4.2x104 ± 2200 IJs/mL and 3.9x104 ± 2000 IJs/mL, respectively. In vitro scale-up technology can be further optimized for production of this biocontrol agent by improving media formulation, process parameters, bioreactor design and inoculation times that will maximize nematode yield. Keywords: