The Screening Study Of High-yield Lipase Strain

Lipase is an enzyme of catalyzing hydrolysis of triglyceride, which catalyzes the hydrolysis of natural substrate oils to produce fatty acids, glycerol and glycerol ester or glycerol diester. The basic unit of lipase is only amino acids, which usually contains one polypeptide chain. Its catalytic activity just depends on the its protein structure. Lipase is an enzyme with multiple catalytic reaction which can be catalyzed triglyceride glycerol and other water-insoluble ester hydrolysis, alcoholysis, esterification, transesterification and ester synthesis of the reverse reaction. The lipase plays different activity characteristics depend on the reaction system, such as in oil-water interface for ester hydrolysis, and enzymatic synthesis in organic phase and transesterification.Lipase is widely found in animals, plants and microorganisms. The properties of lipase include optimal temperature and pH, temperature and pH stability, substrate specificity and other aspects. Microbial lipases can have a wider range of pH and temperature, so we choose the microorganism to produce lipase.Lipase is an important industrial enzyme species and widely used in oil processing, food, pharmaceutical, cosmetic and other industries. Lipase from different sources have different characteristics and catalytic activity catalytic. The lipase with transesterification or esterificationfunction function have an important on the enzymatic synthesis of chiral fine chemicals and compounds.Lipase can increase and improve food flavor and aroma, produce flavor esters, improve the nutritional value of edible oil and increase the varieties of edible oil, improve bread quality and to improve the protein foam, catalytic synthesis of fine chemical products, optical resolution of racemic mixtures and so on.Lipase also play an important role in the production of biodiesel. In recent years, biodiesel, similar to diesel, is a renewable biomass energy. The main component of biodiesel is the fatty acid methyl esters. With the lipase catalyst,alcohols and triglycerides which is important in natural vegetable oils or animal fats transesterification occurs. And methoxy substitute glycerol on the fatty acids to formed three long-chain fatty acid methyl ester, which improve the performance of oil viscosity and gasification and make it suitable to the fuel requirements.From Soil, Restaurant vent hood,slaughter houses sewers and hotel sewage pond collected about 160 soil samples, 14 lipase-producing strains are isolated through Rhodamine B instructions flat preliminary screening and shake flask rescreening. The highest yield is 6.75U/mL and we make it as the wild strain to mutagenesis breeding.Through the strain's colony morphology, single-cell morphology and physiological and biochemical characteristics and according the <>, we name it Geotrichum candidum L-8.By UV-photoreactivation Mutation, the Geotrichum candidum L-8 produce lipase to 12.08U/mL and incresed 78.96% compared with original production.The culture and fermentation conditions is optimized according the optimization of single-factor, Plackett-burman design optimization and Response surface design optimization, and we get the lipase production of 27.96U/mL. At the same time, the best medium composition: wheat bran 5%, soybean oil 1.4%, corn steep powder 5%, potassium hydrogen phosphate 0.6%, potassium chloride 0.1%, sodium nitrate 0.4%, magnesium sulfate 0.3% and the optimum fermentation conditions: at 30℃, 110 rpm, 30mL per flask(250mL) foster 24h.Finally, through studying the properties of Geotrichum candidum L-8 lipase, the optimum temperature and pH for enzyme is 30℃and pH 7.0. So we make sure that the Geotrichum candidum L-8 can produce low temperature and neutral lipase.