The pattern of biosurfactant production from naphthalene in cultures inoculated with washed 19SJ cells was very different
from that of cultures inoculated with the whole broth. Biosurfactant production, like cell growth, depends on the availability
of the substrate. Naphthalene solubility (31 mg/liter) was high enough to allow unrestricted growth of both washed and unwashed cells, as illustrated by their similar increase in turbidity(Fig. 2). However, at high cell density, the availability of poorly soluble substrates becomes limiting (40) because PAHs are utilized only in the dissolved state. The fact that glycolipid accumulation started more rapidly when the cultures were inoculated with the whole broth may be partially explained by the concomitant addition of biosurfactants that could increase naphthalene availability and hence bacterial utilization.