Formulation of defined consortia isolated from sediments of the Chao Phraya and tha Chin rivers for removal of petroleum hydrocarbons

Abstract

Recently, Thailand faces petroleum contamination in various environments including Chao Phraya and Tha Chin Rivers, which are the main water transportation resulting in oil spill events on the rivers. The oil used in cargo ship is fuel oil which is the mixtures consisting of polycyclic aromatic hydrocarbons (PAHs), aliphatic, asphalthene, and resin. Therefore, this study aimed to formulate the defined bacterial consortium from the selected effective hydrocarbon-degrading and biosurfactant-producing bacteria which having high cell surface hydrophobicity for removal of petroleum oil. In this study, eight strains having different ability to degrade PAHs and aliphatic compounds were obtained and then three high effective bacteria were selected. Mycobacterium sp. J101 had ability to degrade low- and high-molecular weight PAHs and aliphatic compounds. Rhodococcus ruber S103 degraded aliphatic compounds and had high cell surface hydrophobicity and Mycobacterium sp. Y502 degraded high molecular weight PAHs as well as showed potential to produce biosurfactants. These three individual strains, S103, J101, and Y502 could degrade approximately 20% of fuel oil at 2,000 mg L-1 in liquid cultivation within 7 days. While, the defined consortium composed of these three strains degraded fuel oil at 41%. When this defined consortium was immobilized on bio-balls, the immobilized defined consortium had fuel oil removal efficiency in carbon free mineral medium (CFMM) and freshwater from Chao Phraya river by adsorption ability of bio-balls and biodegradation efficiency of defined consortium. When the fuel oil remaining on bio-balls with and without defined consortium was analyzed, it was found that the concentration of fuel oil on bio-ball having defined consortium (816 mg g-1 bio-ball) was lower than the concentration of fuel oil on sterilized bio-ball (1,523 mg g-1 bio-ball). The immobilized defined consortium was able to degrade 46% of fuel oil within 15 days, whereas no degradation was observed in the experiment without bacteria. Furthermore, the result of 16S rRNA gene amplicon sequencing analysis and viable plate count technique found that immobilized defined consortium could survive throughout the experimental period. Consequently, these results indicated that the immobilized defined consortium had a potential to apply for bioremediation of petroleum oil contaminated in the environment.