observed for the pervaporation index than for the standard mixture.
We believe that the observed increase in the pervaporation
index was due to the presence of lactic acid in the broth. As a result
of the low concentration of this acid observed in the fermentation
broth at 0.75 mmol L1, a decrease was not observed in the enrichment
factor of ethanol, as reported in the work of Chovau et al.
(2011). Thus, because the polydimethylsiloxane membrane is
hydrophobic, the presence of lactic acid increased the hydrophilicity
of the membrane, which increased the flow of water, whereas
the increase in the flow of ethanol can be attributed to the effect
of membrane fouling. Bowen et al. (2007) have confirmed these
statements in their studies