 The efficiency of removal can be optimized by treating the EPSs with different acids or bases before adding them to wastewater.Some contaminated soils contain high levels of polycyclic aromatic hydrocarbons (PAHs); EPSs from the bacterium "Zoogloea" sp.and the fungus "Aspergillus niger", are efficient at removing these toxic compounds.EPSs contain enzymes such as oxidoreductase and hydrolase, which are capable of degrading PAHs.