Effect of inoculum age and physical parameters onin vitroculture of the entomopathogenic nematodeSteinernema feltiae

Abstract

Entomopathogenic nematodes (EPNs) of the families Steinernematidae and Heterorhabditidae have a symbiotic association with bacteria which makes them virulent against insects. EPNs have been mass produced using in vivo and in vitro methods, including both solid and liquid fermentation. This study assessed the effect of nematode inoculum age on the production of Steinernema feltiae in liquid, solid and biphasic processes. Several physical parameters were also assessed: the effect of medium viscosity, flask size and aeration speed on the recovery and yield of infective juveniles (IJs). Inoculum age treatments included inoculum liquid cultures that were 7, 14, 21 and 28 days old. Nematodes from the same inoculum were added to one liquid medium (liquid culture), one solid medium with bacteria previously grown in sponge (solid culture) and a variation of the solid medium (a biphasic culture), in which the bacteria were first grown in liquid and, then, soaked into the sponges, with the purpose of providing a more homogeneous bacterial culture before nematode inoculation. Experiments were conducted in Erlenmeyer flasks. Eight treatments were established involving combinations of three variables: two media (with and without 0.2% agar), two flask sizes (250 and 150 ml) and two agitation speeds (180 and 280 rpm). The study showed increases in nematode yield for liquid cultures, but not for solid or biphasic cultures, with the advance of the inoculum age up to 28 days of growth. Furthermore, the addition of 0.2% agar to the liquid medium and increasing the aeration rate by using larger flasks with higher agitation speed may increase nematode recovery and final yield. The experiments were conducted using shake flasks but the results may also be applicable for bioreactors.

Cultivation of the gut bacterium Prevotella copri DSM 18205T using glucose and xylose as carbon sources

“…The duration of the lag phase and the shape of the exponential phase in the growth curve have been reported to depend on the physiological state of the cells in the inoculum, for example, the fraction of viable cells in the inoculum, and the handling of the inoculum cultures (Hornbaek et al, 2004; Leite et al, 2017; Zhang et al, 2002). In this study, only small differences were seen as a consequence of different inoculum sizes, which indicates uniform viability and growth phase in the inoculum.…”

Entomopathogenic Nematodes in Sustainable Food Production

“…However, in certain countries lower labor and raw materials expenses allow solid culture to be highly profitable and it is therefore the chosen method. Several approaches can be used to improve in vitro culture including optimization of media and fermentation characteristics Leite et al, 2017).…”

Production of entomopathogenic nematodes in submerged monoxenic culture: A review

“…According to Leite et al (2017), the yield productivity (121 × 10 3 -178 × 10 3 nematodes/ml) of S. feltiae during liquid culture in Erlenmeyer flasks follows an increasing linear relationship with inoculum age (7-28 days). Based on this study, 7 days after inoculation, 65% of the IJs were formed as adults, and the best yield productivity was achieved using a 28-day old inoculum.…”