Journal of Petroleum & Environmental Biotechnology

Abstract

Bacterial Degradation of the Saturate Fraction of Arabian Light Crude oil: Biosurfactant Production and the Effect of ZnO Nanoparticles

Wael Ismail, Noora A Alhamad, Wael S El- Sayed, Ashraf M El Nayal, Yin-Ru Chiang and Riyad Y Hamzah

The aim of this research was to study the influence of nanoparticles and the initial oil amount on the biodegradation of crude oil. Production of biosurfactants was also assessed. Crude oil-utilizing bacteria were isolated from oilfields via enrichment in chemically defined medium with crude oil a sole carbon source. The isolates could be affiliated to the genera Bacillus, Pseudomonas, Achromobacter, and Microbacterium by 16S rDNA sequencing and phylogenetic analysis. GC/FID analysis revealed 52 to 98% degradation of the oil saturate fraction within one month. Nanoparticles of ZnO inhibited growth and crude oil biodegradation by one isolate. (NBHCO4). Two strains, NBHCO2 and NCEOW, emulsified and utilized water-in-oil emulsions (chocolate mousse). Two bacterial strains, I-19 and NBHCO2 grew with crude oil in cultures containing up to 20% oil. Degradation extent in the I-19 culture increased as the oil amount increased. On the contrary, the NBHCO2 culture exhibited a decrease in degradation extent as the oil amount increased. Biosurfactant production in only one crude oil culture (I-19) could be confirmed by the observed reduction in surface tension. Some isolates produced biosurfactants from water-soluble substrates such as glucose. The NBHCO2 strain produced a lipopeptide biosurfactant which reduced the surface tension of the growth medium from 72 to 27mN/m. A gene of catechol dioxygenase was detected in the I-19, NBHCO4, and NCEOW isolates. In conclusion, metal oxide nanoparticles can interfere with crude oil biodegradation. Biosurfactants are not necessarily a prerequisite for crude oil biodegradation. The initial oil amount is a significant determinant of oil biodegradability. The isolates can by applied for bioaugmentation of petroleum-polluted soil and biosurfactants production.