A review of the in vitro liquid mass culture of entomopathogenic nematodes

Abstract

Entomopathogenic nematodes (EPNs) are a safe insect biological control agent. Key to the implementation of EPNs as a biopesticide is their mass production in shake flasks and bioreactors. For commercial application, in vitro liquid culture is the predominant choice, due to the cost and scale of production, and to the ease of downstreaming. The in vitro liquid culture of EPNs begins in Erlenmeyer shake flasks to provide aeration and agitation. The initial liquid culture phase is followed by upscaling to 5-20-L desktop bioreactors and, thereafter, to 80-120-1000-L industrial-scale bioreactors. The ingredients of the liquid culture media, on which symbiotic bacteria and nematode develop, is of great importance for mass-culturing. The diet usually consists of essential nutrients that best replicate the constituency of the natural insect host, such as protein, carbohydrates and lipids. In addition, aeration and agitation are maintained, without causing shear damage due to the rotating impeller blades. Such factors, however, requires different parameters, depending on the EPN species involved, and, moreover, optimisation is required to obtain high yields and quality of infective juveniles. The objective of the current review is to assess the conditions required for optimal EPN production in liquid culture, and how the conditions might be optimised for South African EPN species. © 2020 Informa UK Limited, trading as Taylor & Francis Group.