Biodegradation of Heavy Oil from the Nakhodka Oil Spill by Indigenous Microbial Consortia

A biodegradation process of heavy oil from the Nakhodka oil spill by indigenous microbial consortia was monitored over the 429-day at laboratory scale. The indigenous microbial consortia consisted of bacteria and fungi from the Nakhodka oil spill in the Sea of Japan as well as the bacterium Pseudomonas aeruginosa isolated from Atake seashore, Ishikawa Prefecture, Japan. Both bacteria and fungi had a significant role in the observed biodegradation of heavy oil during the 429-day bioremediation of the Nakhodka oil spill with respect to the pH of the solution. Hydrocarbon-degrading bacteria had tendency to play greatest role at the neutral-alkaline condition (pH: 7~7.8). On the contrary, when pH shifted to acidic (pH: 2~4), the fungi took over to degrade heavy oil. Fungal succession during the 429-day bioremediation was predominated by Rhinocladiella sp., while all fungi which survived in degrading heavy oil were identified as Rhinocladiella sp., Aspergillus sp., Acremonium sp., and Penicillium sp. During that period, the aliphatic hydrocarbons were reduced significantly, whereas the aromatic hydrocarbons remained relatively constant, and there was the production of metabolites after 429 days of bioremediation. These results suggest that both bacteria and fungi as indigenous mixed microbial consortia may contribute to the biodegradation of heavy oil from the Nakhodka oil spill. In addition, the benevolent and favorable microbial interactions in bioremediation are essential and requisite to completely biodegrade oil spills for bioremediation success.