Hwai-Shen Liu
Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan 106
An alkane-biodegrading bacterium identified as Rhodococcus erythropolis (NTU-1 strain) was isolated from petroleum-contaminated soil. When long-chain alkanes are supplied as the carbon source, NTU-1 tends to form pellets, ranging from 0.1 to 2 cm in diameter, and thus remove significant amount of alkanes by biodegradation and physical trapping in a short period. Quantitatively, more than 95% of each alkane (~2000ppmv) could be efficiently removed within 40–68 h. Further, Rhodococcus erythropolis strain NTU-1 was also confirmed to be able to degrade C10–C32 n-alkanes in diesel oil or crude oil. While degrading these n-alkanes, NTU-1 also trapped most other non-degradable oil constitutes in pellets. In batch cultures with 10,000ppmv diesel or crude oil, approximately 90% oil removal was achieved within 4 days. In bioreactors with aeration and pH adjustment, an intermittent feed of 42,000ppmv n-hexadecane resulted in approximately 87% removal within 4 weeks and an intermittent feed of 35,000ppmv diesel or crude oil resulted in more than 90% removal within 2 weeks.
It was also found that, if NTU-1 was properly cultured and heat-dried, the cells could work as bio-flocculating agent that could shorten the clean up time to 12h, as compared to 40-68h. Meanwhile, the cells further showed good capability to de-emulsify oil/water/surfactant emulsion system and may play a role in separate oil from tertiary recovery in petroleum industry.
These interesting and versatile phenomena of Rhodococcus erythropolis NTU-1 involving bio-degradation, bioflocculation and bio-demulsification will be presented and discussed.