Screening Of High-yield Lipase Strains And Discovery Of Enzymology Character

Lipase is a special hydrolase, which can decompose the fat into glycerol and fatty acids. Lipase is widely found in plants, animals and microorganisms, and it can also be obtained by chemical synthesis. The most of lipase is produced by microbial fermentation. The reasons are as follows:The source of animals and plants can be affected by climate and soil, and the high cost is paid in the process of chemical synthesis. At present, these bacteriers can produce lipase, including Aspergillus niger, Geotrichum candidum, Pseudomonas, Mucor, Rhizopus, Candida, etc. Lipase are widely used in industrial production, such as washing, food industry, pharmaceuticals industry, chemical industry, leather industry, paper industry and so on. Therefore, it shows great development and potential economic value to obtain a high-yield strains of lipase.In this study, four strains are isolated from the microorganisms in water, which is defined as strain 3, strain 5, strain 6 and strain 7. And the activeties of lipase from four strains are respectively 3.00U/mL,1.70U/mL,1.70U/mL,4.00U/mL.The fermentation conditions of strain 7 were investgated, and the optimized fermentation condition was:pH 7.0,25℃for 72 h. According to the morphological, physiological biochemical identification and 16SrRNA sequence analysis, this strain belonged to Pseudomonas and named as strain 7.Before lipase was purified, the pI of lipase was determined 6.0 and the range of ammonium sulphate fractional precipitation was 40-50%.The lipase of supernatant was separated through ammonium sulphate fractional precipitation, desalting, DEAE-Sepharose Fast Flow, freeze-drying, and Sephadex G-75.The molecular weight of lipase was 31ku by SDS-PAGE. Furthermore, the characteristics of crude lipase was investigated. The result showed tant its optimal pH was 9.0, and its optimal temperature was 20℃. The lipase had a wide range of pH and temperature, and it showed more stable in pH8.0,30-50℃. The lipase activity was stimulated by Li+, Mg2+, Ba2+ tween 80 and Triton-100, while inhibited by EDTA and Ethyl acetate at the concentration of 1 mmol/L. Moreover, the lipase was resistant to alcohol.