Immobilization Of Lipase Onto Nanofibrous Membrane For Fabricating High Performance EMBR

Enzyme-immobilized membrane bioreactors(EMBR) can create a favorable thermodynamics and kinetics process by combining the high selectivity of enzymatic reaction and high efficiency of membrane separation,which provide high reaction rate as well as low operation cost,and therefore have been widely applied in numerous fields of food,pharmaceutical,and detergent industries.The activity of immobilized enzyme and the reactor structure play a significant role in the performance of EMBR.Considering these,in this thesis,cellulose fibrous membrane was used as enzyme-immobilized support to improve the properties of immobilized lipase.Furthermore,a biphasic EMBR based on the lipaseimmobilized fibrous membrane was designed and optimized.The relative experiments and results are summarized as follow.Cellulose acetate(CA) nonwoven fibrous membrane was prepared by electrospinning,followed by alkaline hydrolysis to obtain regenerated cellulose (RC) nonwoven fibrous membrane.Electrospinning conditions were systematically studied.Surface morphologies and chemistry of the membrane during the deacetylation process were monitored with field emission electron microscopy (FESEM),attenuated total reflectance floufier transform infrared spectroscopy (ATR/FT-IR) and titration experiment.It was found that the deacetylation of CA fibrous membrane was efficient and complete.The RC fibrous membrane was oxidized by NaIO₄ to simultaneously generate aldehyde groups,and then reacted with pentaethylenehexamine(PEHA).Lipase was immobilized onto the modified fibrous membrane using glutaradehyde(GA) as coupling agent.Response surface methodology(RSM) was applied to model and optimize the immobilization conditions.It was observed that,at the optimal condition,the immobilized-lipase retained 54.33%of the free enzymatic activity. Furthermore,the immobilized-lipase exhibited significantly higher stability than the free form.Based on the above work,a biphasic EMBR was assembled with the lipase-immobilized fibrous membrane.Effect of operating variables(namely aqueous solution,pH,sodium taurocholate hydrate concentration,temperature and membrane usage) on the performance of this biphasic EMBR was investigated with the hydrolysis of olive oil.It was found that,at the optimal operational condition, an activity of about 9.83×10⁴ U/m² can be obtained.