DEVELOPMENT OF LIQUID BACTERIAL FORMULATION OF Exiguobacterium sp. AO-11 FOR BIOREMEDIATION OF CRUDE OIL CONTAMINATED SEAWATER

Abstract

Bioremediation is an effective, low cost and environmental friendly technique to clean up crude oil-contaminated environment. This study aimed to develop the ready to use liquid bacterial formulation of petroleum hydrocarbon-degrading Exiguobacterium sp. AO-11 which was isolated from marine sediment, for bioremediation of crude oil contaminated-seawater. Strain AO-11 was evaluated for the degradation of crude oil in various environmental conditions. The results revealed that this strain could degrade crude oil in various environmental conditions including pH 6 to 9, salinity 8 to 45.4 ppt, temperature 25 to 37oC and crude oil concentration 0.25 to 1.5% (v/v). In order to reduce the cost of bacterial formulation, agro-industrial byproducts, soybean oil mill dry sludge 15% (w/v) (SB) in 1:4 diluted seawater based medium was used for bacterial cultivation and it could enhance bacterial cell growth from 6.07±0.06 Log CFU/ml up to 8.6±0.02 Log CFU/ml in 9 hours. For preparation of liquid formulation, phosphate buffer was selected as a suitable suspension solution which could preserve AO-11 survival at 86.7±1.4% in 30 days and maintain crude oil degradation in liquid cultivation at more than 80%. Protective agent (PEG 1%) was selected for prolonged storage and it could preserve AO-11 up to 72.4±0.2% and 58.7±0.7% at 4ºC and 30ºC in 60 days, respectively. The preliminary estimation of the costs of AO-11 liquid formulation was at 68 baht/L. Moreover, 30-day stored AO-11 formulation could degrade 0.5% (v/v) crude oil in seawater up to 61±5.2%. This study revealed the potential of using agro-industrial waste based cultivation medium for bacterial cell production. Furthermore, liquid bacterial formulation was developed and it has potential to be used for bioremediation of crude oil-contaminated seawater.