Biodegradation of oil wastewater by free and immobilized Yarrowia lipolytica W29.

The ability of Yarrowia lipolytica W29 immobilized by calcium alginate to degrade oil and chemical oxygen demand (COD) was examined. The degradation rules of oil and COD by immobilized cells with the cell density of 6.65 x 106 CFU/mL degraded 2000 mg/L oil and 2000 mg/L COD within 50 h at 30 degrees C (pH 7.0, 150 r/min), similarly to those of free cells, and the degradation efficiencies of oil and COD by immobilized cells were above 80%, respectively. The factors affecting oil and COD degradation by immobilized cells were investigated, the results showed that immobilized cells had high thermostability compared to that of free cells, and substrate concentration significantly affected degrading ability of immobilized cells. Storage stability and reusability tests revealed that the oil degradation ability of immobilized cells was stable after storing at 4 degrees C for 30 d and reuse for 12 times, respectively, the COD degradation rate of immobilized cells was also maintained 82% at the sixth cycle. These results suggested that immobilized Y. lipolytica might be applicable to a wastewater treatment system for the removal of oil and COD.