Orange waste resulting from juice processing that contains a high level of fermentescible sugars was utilized as a basal medium at 2% (w/v) for the production of alpha-amylase (E.C.3.2.1.1) using a fungal strain of Aspergillus oryzae (Ahlburg) Cohen 1042.72, at 30 degreesC on a rotary shaker. The production of the alpha-amylase, proteins and biomass was achieved using the statistical method of [Plackett-Burman design at N = 12, namely 12 experiments and I I factors (7 real values and 4 dummy)]. Statistical analysis showed the following results: (a) the variation of starch concentration (0 at 2%), of yeast extract (0 at 0.5%) and of "Corn steep liquor" (0 at 2%) has a positive effect which is highly significant on the production of a-amylase and proteins with the following probabilities respectively (p greater than or equal to 80-95%, p greater than or equal to 80-95%, p greater than or equal to 70-991%). (b) as for biomass, it seems that it is positively affected by the variation of starch (p greater than or equal to 95%), "Corn steep liquor" (p greater than or equal to 95%) and agitation (150-200 rpm) (p greater than or equal to 80%). (c) the salt utilized (MgSO4, 7H(2)O 0 at 0.5 g/l, MnSO4 0 at 0.1 g/l, FeSO4 0 at 0.1 g/l, ZnSO4 0 at 0.02 g/l) showed a negative effect which is highly significant (P greater than or equal to 80%) on the production of proteins and without effect on the two previous responses (enzyme production and biomass). On conclusion, the statistical analysis allowed the selection of factors such as starch, yeast extract, "Corn steep liquor" and a low concentration of salt. (C) 2003 Elsevier Ltd. All rights reserved.