aerate

Experimental runs were in triplicate, conducted without aeration and for air flow rates of: 40, 60, 100, 120 and 200 ([cm.sup.3.sub.air] [g.sup.-1.sub.substrate] [h.sup.-1]).

Tables 1 and 2 report that, with the exception of the results for aeration equal to 40 [cm.sup.3.sub.air] g1substrate h-1, higher values of the emulsification activity correspond to the Aspergillus fumigatus SSF process with no additional hydrocarbon sources.

Experimental results in Table 1 and 2 reveal a strong dependence of the emulsification activity on the aeration all through the process of biosurfactants production by Aspergillus fumigatus SSF.

Therefore, the time and the aeration are the two independent variables to be considered for the mathematical modeling.

where [B.sub.1] to [B.sub.6] are numerical coefficients to be determined and Z = sin[[a.sub.1].log([a.sub.2]xV)] is a new function, accounting for the effects of aeration (V) on the biosurfactants production.