Abstract:
The oil spill in the Gulf of Thailand, off the coast of Samet Island in July 2013 is regarded as one of the serious environmental disasters in Thailand, especially in Ao Phrao, Samet Island. The aim of this study is to isolate crude oil-degrading bacteria and examine its ability to remediate crude oil-contaminated sandy soil. Soil and sediment samples used in this study were collected approximately one week and one month after the oil spill incident. These samples were collected from twelve locations near Ao Phrao beach. Indigenous crude oil-degrading bacterial consortia can be enriched by using 0.25% (v/v) crude oil as the sole carbon source. Due to the limitation of consortia, individual bacterial strains showing crude oil degradation ability were isolated from the consortia and identified by 16S rDNA sequence analysis. As a result, Exiguobacterium sp. AO-11 capable of degrading 91.6% of 0.25% (v/v) crude oil within 10 days was the most efficient strain in this study. Because of its characteristics that enhanced capable of degrading crude oil and non-pathogenicity, Exiguobacterium sp. AO-11 could be the potential candidate for remediation of 4% (w/w) crude oil-contaminated sandy soil.The results of 16S Metagenomic analysis indicated that Exiguobacterium sp. AO-11 was detected only at days 20. As this strain plays the role in degradation of long-chain alkane and medium-chain alkane, this characteristic could enhance the growth of other crude oil-degrading bacterial strains. Nevertheless, the result indicated that the addition of Exiguobacterium sp. AO-11, nutrient and dispersant could increase the crude oil degradation efficiency. Therefore, the combination of three treatments, Bioaugmentation Biostimulation and Dispersant, was appropriate approach for the remediation of crude oil contaminated sandy soil.