Effect Of Metal Ions On The Enzymatic Hydrolysis Of Hemp Seed Oilby Lipase Candida Sp.99-125

Fatty acid is an important energy provider for human,and it is one of the basic components of organism.Unsaturated fatty acid plays an important role in membrane function,regulating immune system,the adjusting maintain brain function and cardiovascular disease,cancer,etc.Hemp?Cannabis sativa L.?seed oil is considered to be an important functional and nutritional vegetable oil because of its high contents of two polyunsaturated essential fatty acids?EFAs?.Oil hydrolysis is an important approach to the preparation of fatty acid.Comparing with high energy and pollution of physical method and chemical hydrolysis method,enzymatic hydrolysis method is high efficiency and environmental friendly.This article combined with spectroscopy analysis method studied the change of lipase conformation,enzyme activity,thermal stability,response speed and selectivity by metal ions through lipase hydrolysis hemp seed oil.In order to study the effect of metal ions on Candida sp.99-125 lipase,firstly,the spectroscopy study were investigated in presence of Ca²⁺,Mg²⁺,Fe²⁺,Fe³⁺,Cu²⁺,Sn²⁺,Pb²⁺,Zn²⁺,Ba²⁺metal ions,respectively.The UV spectroscopy results showed that all the metal ions enhanced the absorbance intensity.Thefluorescence spectra results displayed similar trend except Fe³⁺,which decreased the fluorescence intensity.Synchronous fluorescence spectroscopy results showed that the contrary results with UV spectroscopy,which is all the metal ions decrease the fluorescence intensity.In order to find the high efficiency and low cost reaction condition of Candida sp.99-125 lipase hydrolysis hemp seed oil,single factor and response surface optimization method had been used.And the result showed that: the optimal conditions of the reaction were temperature 45?,pH 8.2,water-oil ratio?w/w?0.47g/g,and enzyme-oil ratio 0.70%.Candida sp.99-125 lipase enzyme activity and thermal stability had been tested by olive oil emulsification method.The results showed that metal ions had significant influence in enzyme activity and thermal stability.All the metal ions could improve the lipase thermal stabilityexcept Cu²⁺.Among that Sn²⁺,Fe³⁺ ions showed the highest improvement in thermal stability.The last part of this paper studied the effect of the interaction of Candida sp.99-125 lipase and metal ions on hydrolyze hemp seed oil.The initial rate study of hydrolysis experiment showed that metal ions did not improve the initial rate of hydrolysis in the first 10 min.After 3h,Ba²⁺ group showed highest hydrolysis rate which is almost 30% higher than control group.After 72 h,Ca²⁺,Fe³⁺,Pb²⁺,Ba²⁺ group all showed improve effect on hydrolysis rate.The study of GC analysis on hydrolysis product showed that metal ions could change lipase selectivity in some degree,Ca²⁺,Fe³⁺ ions could improve around 5% linolenic acid contend.This thesis made an initial exploration on the study of the metal ions influences of Candida sp.99-125 lipase on the spectroscopy study,thermal stability,hydrolysis rate and the selectivity.It offers effective information for the preparation of fatty acid,glycerol and biodiesel by industrial enzyme method.