| Microbial lipase, as biocatalyst, were widely used in many industrial fields. Much work was paid to improve the production and stability of microbial lipases, which had became a hot point all over the world.A strain of lipase producing microbial were isolated form nature which was idntified as Acinetobacter sp. according to its morphology, physiological and biochemical properties as well as its 16S rDNA sequence analysis and named as Acinetobacter sp. SYBC Li-2.Electrophoretic pure enzyme on the SDS-PAGE was obtained through ammonium sulfate precipitation and PEG/phosphate aqueous two-phase system extraction. The lipase of SYBC Li-2 was 8.64 times after purified and the recovery was 38.97%. Employing SDS-PAGE the only subunit of the lipase was known and the molecular mass was determined to be 24.5kDa.The lipase of SYBC Li-2 was metal-ion binding enzyme, the enzyme activity increased by 39.1% thanks to the exist of Ca2+ at the concentration of 5 mmol/L, however, calcium was not essential to enzyme actvity.The lipase of SYBC Li-2 was steady at 40℃and 50℃except 60℃. The lipase of SYBC Li-2 was steady at the pH range from 7.0 to 9.0, and the most steady pH is 8.0. After 1 h incubation at pH5.0, the retained relative enzyme activity was about 50%. Addition of 5 mmol/L Ca2+ could enhance the enzyme thermal stability at 60℃: after 1 h incubation, the retained relative enzyme activity was 68% comparing to 43% which was the retained relative enzyme activity without Ca2+. However, the same action had no effects on the enzyme pH stablilty.The yield of enzyme was significantly improved by adding of Ca2+ at the concentration of 5 mmol/L at the beginning of flask incubation and the enzyme production was inhibited by addition of La3+ or Trifluoperazine. What is more, the effect of calcium on flask incubation was more abvious to that on the purified enzyme, indicating that calcium could not only activiate the enzyme but also stimulate the secretion of lipase during the flask incubation.
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