A Low-Cost Technology for Entomopathogenic Nematode Large-Scale Production

Abstract

Entomopathogenic nematodes of the genera Steinemema and Heterorhabditis may provide a valuable alternative to chemical insecticides. The characteristics that make them excellent biopesticides include their wide host spectrum, the ability to search for and kill hosts rapidly, and their high virulence and reproductive rates. Furthermore, they are considered environmentally safe. The major constraint to overcome before the onset of commercialisation is their mass production. Entomopathogenic nematodes are currently mass-produced in vivo or in vitro, either in solid culture or in liquid cultivation. An overview of these mass production methods and an analysis of three different bioreactor designs are presented. The progress achieved in liquid culture due to an improvement on sexual contact between adults (better mixture of the solid phase), which results in higher yields (RF), as compared with those reported before, is demonstrated. This improvement in the area of bioreaction engineering allowed these biopesticides to become more competitive compared to chemical insecticides. However, further technological advances and biological studies towards a better understanding of physiology and genetics of the complex nematode-bacterium are still required.

Production of entomopathogenic nematodes in submerged monoxenic culture: A review

“…In contrast, yield production of S. carpocapsae in an airlift bioreactor with external recirculation and working volume of 0.5 L follows a decreasing relationship at aeration rates of 0.05 and 0.15 vvm, suggesting that low airflow rates promote heterogeneous distributions of female and male adult nematodes in the vessel (Neves, Simões et al, 2001;Neves, Teixeira et al, 2001). In this sense, the di- (Chavarría-Hernández et al, 2007).…”

“…In mechanically agitated airlift bioreactors, the mixing is favored by the use of proper impellers and an inner cylinder (Chavarría‐Hernández et al, 2007, 2010, 2011; Chisti & Jauregui‐Haza, 2002; Ehlers et al,1998; Strauch & Ehlers, 2000). In pneumatically agitated airlift bioreactors, the flow‐through internal or external channels is due to the gas injection (Neves, Simões et al, 2001; Neves, Teixeira et al, 2001).…”

“…The EPN culture broth is a gas–liquid–solid system. In the first approach, nematodes were considered the solid phase, the dissolved nutrients in the broth, the liquid phase, and the air bubbles the gaseous phase (Neves, Simões et al, 2001). However, recent studies show that the liquid phase contains ingredients suspended at the beginning of the process, such as 350‐µm coagulate egg yolk particles and vegetal oil droplets (Pérez‐Campos et al, 2019).…”

“…In cultures of H. megidis in 5–10‐L stirred tanks and 40% controlled saturation of DO, increasing aeration rates from 0.3 and 0.7 air‐volumes per liquid‐volume per minute (vvm) doubling the IJ production, and this could happen because of secondary metabolites that are negative for nematode survival were exported out of the liquid phase, which favors the reproduction (Strauch & Ehlers, 2000). In contrast, yield production of S. carpocapsae in an airlift bioreactor with external recirculation and working volume of 0.5 L follows a decreasing relationship at aeration rates of 0.05 and 0.15 vvm, suggesting that low airflow rates promote heterogeneous distributions of female and male adult nematodes in the vessel (Neves, Simões et al, 2001; Neves, Teixeira et al, 2001). In this sense, the dimensionless Reynolds number was used as an index of hydrodynamic conditions within a pneumatically agitated bioreactor, where D H is the hydraulic diameter, is the superficial gas velocity in two sections, is the culture broth density, and represents the apparent viscosity.…”

“…The biotechnological challenge to improve the performance of the culture process makes it necessary the control of physiology of symbiotic bacteria, formulation of culture medium (Chavarría‐Hernández, Espino‐García, Sanjuan‐Galindo, & Rodríguez‐Hernández, 2006; Islas‐López, Sanjuan‐Galindo, Rodríguez‐Hernández, & Chavarría‐Hernández, 2005; Leite, Shapiro‐Ilan, Hazir, & Jackson, 2016a; Masurekar, 2008; Yoo, Brown, Cohen, & Gaugler, 2001), and process parameters, such as oxygen transfer rate, temperature, pH (Ferreira, Addison, & Malan, 2016), inoculum size and timing of inoculation (Johnigk, Ecke, Poehling, & Ehlers, 2004), EPN sensitivity to shear and normal stresses, IJ recovery, geometry, and configuration of the bioreactor (Chavarría‐Hernández, Sanjuan‐Galindo, Rodríguez‐Pastrana, Medina‐Torres, & Rodríguez‐Hernández, 2007; Neves, Simões, & Mota, 2001) among others.…”