Kokou D. ADJALLÉ) - INRS

plan (CCP) and the response strface method (RSM). The spray drying operational parameters
(inlet temperature, flow of aspiration of hot air, atomization pressure and feed rate) constitute
independent variables, whereas the outlet temperature, moisture content, number of viable
spores and entomotoxicity are dependent variables. It should be noted that to accomplish all the
objectives of this study, total cells, viable spores, insecticidal potential (entomotoxicity) and
er.zymatic activity are the variables of measurement and analysis of the results.
For the first objective (ultrafiltration), the results showed that a membrane of 5 kDa (pore
diameter of 0.015 pm) with a surface area of 0.1 m2 was optimal for concentration of all
composants present in supernatant, especially the virulence factors (enzymes, vegetative
insecticidal proteins, zwittermicin-A) which play a significant role in the entomotoxicity of the
biopesticides. Efficiency of ultrafiltration in terms of entomotoxicity recovery for soya, SIW,
NH and TH were 100%with entomotoxicity values of I 1.6, 14.6, 13.5 and 9.5 (x 10e SBU/L) in
the respective retentates. The evaluation of the effects of virulence factors (proteases and
chitinases) for a ratio of the centrifugate-retentate, (4g of centrifugate + lmI- of retentate) gave
an increase in the entomotoxicity of 4.3 ,1.6,1.4 and 4.8 (10 e SBU/L) for soya, SIW, NH and
TH, respectively. Meanwhile, there were losses of active components on the ultrafiltration
membrane through the adsorption of matter on the membrane, necessitating further experiments
on membrane fouling.
The retention of organic matter, via physical adsorption on the membrane, is very high for the
supernatants of hydrolyzed sludges (68% of the suspended matter as compared to l5yo, l2yo,
70Â for soya, SIW and NH, respectively). Taking into account the preceding results and
objectives of this work, the membrane fouling study was performed for 0.2 fif membrane with
a volume V (2 L and 4 L) of supernatants of SIW and TH. The results showed that increase in
fouling of the membrane evaluated through the variation of the flow of permeate presented a
stationary phase in ivhich apparent resistance of the fouled layer was maximum. This resistance,
calculated for 2 L of filtration, was 3.5x1012 and 1.8x1012 1m-1; for SIW and TH, respectively.
These values were I .2xl} 12for SIW and 2.lxl0 t:1--t; for TH in the case of 4 L of filtration.
XXVI