UNIVERSITÉ PAUL CÉZANNE, AIX MARSEILLE III - IMEP

Résultats et discussion. Chapitre 3: Evaluation des facteurs de croissance
ergosterol analysis as reported previously. At least three Erlenmeyers flasks per treatment
were evaluated.
Table 1. Mixing ratio of olive twigs and leaves (OTL), olive cake (OC) and olive mill
wastewater (OMW) used as substrate for L.edodes growth.
Treatment No Ingredient
OTL (%) Olive cake (%) OMW (%)
1 0 50 50
2 20 30 50
3 30 20 50
4 50 0 50
2.4. Experimental methodology
2.4.1. Asymmetrical screening design
For systems with a great number of variables different approaches of experimental
factorial designs can be applied to achieve a screening of critical variables and to estimate
their main effects on the responses. Inspiration was drawn from previous works (Baçaoui et
al., 2001; Alinsafi et al., 2005; El Hajjouji et al., 2008). In this study, a 2 5 5 1 //16 experimental
design was processed using Nemrodw software (Mathieu et al., 2000). It allowed the
investigation of six factors (A-F) in sixteen experiments, five factors A-E each at two levels
and one factor F at five levels. Tables 2 and 3 listed the values given to each factor; the choice
was based on our preliminary experiments. Table 4 showed the 2 5 5 1 //16 experimental design.
The results treatment was processed using Nemrodw software.
From the 16 runs we can compute, using the least square method (Baçaoui et al., 2001;
El Hajjouji et al., 2008), the ‘‘weight’’ of each factor level. For each factor, the weight of
each level is related to the upper level weight, which becomes the ‘‘reference state’’ among
each factor (Mathieu and Phan-Tan-Luu, 1997). The weight describes the factor effects on the
response when changing factor levels with respect to the reference state. The obtained results
are generally presented as histograms which graphically illustrate the variable differential
weights (Lewis et al., 1999).
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