The supernatant of Beauveria bassiana SFB-205 reduced the population of cotton aphid,
Aphis gossypii Glover, with a dosage-dependant manner, which allowed a quality control
(QC) factor to be determined for the evaluation of the supernatant as the first step of
a development. Enzymes were assumed as possible QC factors based on 1) the comparable
aphicidal activity of the supernatant protein pellet to the raw supernatant, 2) the supernatant-induced
degradation of the insect cuticles, observed by transmission electron microscopy,
and 3) the confirmation of enzymes related to the fungal penetration – chitinase, and
the Pr1- and Pr2 proteases – in the supernatant. Finally, from the bioassay with the
enzyme-inhibited supernatants processed by substrate inhibition one by one, decreased
aphicidal activities were observed for all three enzyme-inhibited treatments. This phenomenon,
furthermore, was more remarkable in the chitinase-inhibited supernatant.
This finding provides that those enzymes (and most particularly the chitinase) in the
supernatant were strongly involved in the aphicidal activity. Consequently, the amount
of the chitinase may be used as one of the QC factors to determine the insecticidal activity
of the supernatant of B. bassiana SFB-205 in the optimization of mass production.