Study on the potential of bioproduct development of dominant oil-degrading microorganism in South Vietnam coastal environment
Oil-spills incidents can cause great damage to the environment. Among the technologies applied in oil-spills response, bioremediation is a promising technology and has been applied widely. Bioremediation uses indigenous microorganism with high substrate specificity to degrade the hydrocarbons in oil into nontoxic products such as organic acids, aldehydes, CO2 and H2O. The main purpose of bioremediation is to exclude the pollutants from the environment and minimize their impacts on the ecological system.
Nowadays, bioproducts are used widely in oil-pollution treatment around the world. In Vietnam, the number of studies on the application of these products in coastal oil-pollution is limited. The use of bioproducts with foreign microorganism, enzyme, organic substances can lead to secondary pollution due to insufficient information on the target environment, the natural microorganism communities as well as the composition of spilled oil and the imported microorganisms. The study on the potential of bioproduct development of dominant oil-degrading microorganism in South Vietnam coastal environment was conducted to develop bioproducts using the indigenous microorganism to be used in oil-spill response in Vietnam coastal area.
In this study, oil biodegradation ability of 5 hydrocarbon-degrading microorganism species isolated from the natural environment was analyzed with results as followed: Acinetobacter calcoaceticus anitratus VPI – SD (32.2%), Pseudomonas mendocina VPI – BR (25.4%), Acinetobacter venetianus VPI – VT (24.9%), Pseudomonas pseudoalcaligenes VPI – KG (21.5%), Pseudomonas aeruginosa VPI – MN (13.9%). PAHs-degradation ability of the species ranged from 3.6 to 8.3%. Crude-oil degradation ability of the microorganism in the tests with total petroleum hydrocarbons-TPH fluctuated from 29.5 – 37.2 %, and with n-alkanes 59.8 – 73.6 %. The assemblage of microorganisms can degrade persistent substances such as Pristane, Phytane and n-alkanes up to C41.
Growth kinetics analysis of the microorganism with substances’ concentrations at 20g/l peptone and 10g/l yeast extract revealed the maximum density after 72 hours of culturing (109 CFU/ml). For most of the microorganism species, there was no statistically significant difference in maximum density when cultured at 250C and 300C. Study on the fermentation and powdered bioproducts development of 4 microorganism species was conducted in the conditions as followed: stirring speed 200rpm, fermentation temperature 30oC, pH 7.5-8.5, dissolved oxygen 100% saturated, fermentation period of 72 hours. Biomass from the fermented bacteria solution was collected by centrifugation, then freeze-dried by machine and mixed with powder corn cob carrier to create the powdered bio-products. Powdered corn cob was used as carrier for 4 microorganism species, meeting the standard density of 109 CFU/g. After 12 months, the microorganism density reduced to 106-107 CFU/g. Powdered corn cob can be easily biodegraded completely and does not pose a threat to the environment, with high absorbability and suitable for oil-spill response. The tests on the biodegradation efficiency of the bioproduct using Bach Ho crude oil as substance had results of 63.2% for TPH and 95.5% for n-alkanes. The authors have developed a protocol for bio-product production from oil-degrading microorganism to be used in oil-spill response in Vietnam. The time requirement for production is 1 month, at the price of 800.000vnd – 1.000.000 vnd/kg bioproduct.
The report includes 4 chapters with the following content: Experiments to identify the oil-degrading microorganism assemblage for bio-product development; Fermentation to produce microorganism biomass, Determination of carrier and produce bioproduct; Experiments on the activeness of the bio-product and development of protocol for production.