Most medium formulations for improving culture of
entomopathogenic nematodes (EPN) based on protein
sources have used enriched media like animal feed such as
dried egg yolk, lactalbumin, and liver extract, among
other ingredients. Most results, however, showed unstable
yields and longer production time. Many of the results do
not show the detailed parameters of fermentation. Soy
flour, cotton seed flour, corn gluten meal, casein powder,
soytone, peptone, casein hydrolysates, and lactalbumin
hydrolysate as protein sources were tested to determine
the source to support optimal symbiotic bacteria and
nematode growth. The protein hydrolysates selected did
not improve bacterial cell mass compared with the yeast
extract control, but soy flour was the best, showing 75.1%
recovery and producing more bacterial cell number
(1.4×109/ml) than all other sources. The highest yield
(1.85×105 IJs/ml), yield coefficient (1.67×106 IJs/g medium),
and productivity (1.32×107 IJs/l/day) were also achieved at
enriched medium with soybean protein.

Keywords: soy flour, Heterorhabditis bacteriophora, Photorhabdus luminescens, protein, protein hydrolysate