Screening and optimization of extracellular lipases by Acinetobacter species isolated from oil-contaminated soil in South Korea
A total of 53 strains of bacteria were isolated from oil contaminated soil collected in South Korea. The isolated bacteria were screened using spirit blue agar and Rhodamine-B agar media. Two of the isolated strains exhibited a greater clear zone than the others, indicating higher lipase activity. Therefore, these two strains (BK43 and BK44) were selected and identified based on their morphological and physiological characteristics. The 16S rRNA gene sequencing was also implemented. Phylogenetic analyses based on the results of 16S rRNA gene sequencing revealed that BK43 and BK44 were close in identity to Acinetobacter junii. The optimum pH and temperature for lipase production by BK43 were found to be 6.0 at 30°C, after 24 h of incubation, while BK44 were found to be 6.0 at 25°C, after 12 h of incubation. In addition, increased enzymatic production was obtained when the organisms were cultured in medium supplemented with 1% sucrose as the carbon source. Among the different lipase inducers tested, both strains utilized Tween 80 and produced a great level of extracellular lipase. Overall, the results of the present study demonstrate that the genus Acinetobacter is good for extracellular lipase production under acidic conditions.
Key words: Acinetobacter, lipase, optimization, screening.