Location: Fruit and Tree Nut ResearchTitle: The effects of nutrient concentration, addition of thickeners, and agitation speed on liquid fermentation of Steinernema feltiae
|LEITE, LUIS - Instituto Biologicio - Brazil|
|Shapiro Ilan, David|
|HAZIR, SELCUK - Adnan Mederes University|
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2016
Publication Date: 6/30/2016
Citation: Leite, L., Shapiro Ilan, D.I., Hazir, S., Jackson, M.A. 2016. The effects of nutrient concentration, addition of thickeners, and agitation speed on liquid fermentation of Steinernema feltiae. Journal of Nematology. 48(2):126-133.
Interpretive Summary: Entomopathogenic nematodes, also known as beneficial nematodes, are small worms that can be used as environmentally-friendly bio-insecticides. One barrier to wider usage of these nematodes in insect pest management is the high costs associated with producing the nematodes. Therefore, we are studying methods to improve nematode production and reduce costs. Most nematodes are grown in liquid fermentation tanks. In this study, we investigated the effects of aeration in liquid culture by varying rotation speed. We also investigated the effects of adding small amounts of agar to increase viscosity. We discovered that higher rotations speeds (more aeration) improved nematode yield. Also, moderate quantities of agar increased nematode yield; the higher viscosity probably helped suspend the nematodes in liquid culture, which improved their fitness. These results will help improve mass production of beneficial nematodes. Additional research will be conducted to improve nematode nutrition and quality during liquid fermentation.
Technical Abstract: Therefore, this study was aimed at developing a more suitable liquid media for mass production of Steinernema feltiae, by assessing the effects of nutrient concentration, media viscosity, and agitation speed on infective juvenile (IJ) yield. For all the experiments, the base medium contained yeast extract (2.3%), egg yolk (1.25%), NaCl (0.5%) and corn oil (4%). For the nutrient concentration experiment, we evaluated the base medium versus a modified base medium containing 3 times higher concentrations of yeast extract (6.9%), egg yolk (3.75%) and corn oil (12%). The addition of three times more nutrients relative to the base medium resulted in a significantly lower yield of nematodes. For viscosity and agitation speed experiments, five levels of medium viscosity (0.2%, 0.4%, 0.6%, and 0.8% agar) and two agitation speeds (180 and 280 rpm) were evaluated for production. Increasing agitation speed from 180 to 280 rpm and higher levels of agar in the medium (> 0.2%) significantly increased the yield of bacteria. At the lower agitation speed, media amended with 0.4% and 0.6% agar produced higher nematode yields compared to media without agar. Media with 0.2% and 0.8% agar resulted in intermediate levels of nematode production. At the higher agitation speed, media supplemented with 0.8% agar resulted in the lowest yield of nematodes when compared to the other media tested. In conclusion, results indicated that increasing nutrient concentration levels was detrimental to nematode production. Also, media containing agar (0.4% and 0.6%) increased nematode yields when cultures were grown at low agitation speed. When IJs were used as the inoculum, 0.2% agar also enhanced recovery and nematode yield at the higher agitation speed.