Study Onmodificationof PLA Film And Its Application On Immobilization Of Lipase

Poly lactic acid (PLA) film by both PCL and polyethylene glycol (PEG) prepared, the PCL and PEG were used as plasticizers in order to improve the structure and properties of PLA materials and expand the application areas of PLA. And adding the amount of the plasticizer on the structure and properties of the composite membranes were studied. The PLA/PEG membrane can be used as lipase immobilized carrier material for its unique structure, good biocompatibility.PLA/PCL membranes were prepared by solution casting and add ratio(w/w) were 8/2, 6/4,5/5,4/6,2/8, respectively. Effects of PLA/PCL ratio on thermal properties, mechanical properties, hydrophilcity as well as morphology of the composite membranes were investigated. As the result showed, PLA/PCL film is hydrophobic surface. Their tensile strength and elastic modulus increase PCL addition gradually reduced, but the elongation at break increased from 2.7% to 3.6%, much higher than the PCL or less (62.5%), which suggests that blending modification reduced the PLA/PCL film’s mechanical strength but did not effectively improve its toughening effect.PLA/PEG membranes were prepared by add ratio (w/w) of 9/1,8/2,7/3,6/4 and PEG molecular weight of 400,1000,4000 and 1000, respectively. As the result showed, adding PEG can improve mechanical properties and hydrophilicity of membrane. The elongation at break gradually increased with the increasing addition of PEG, but that their tensile strength gradually reduced with the increasing addition of PEG. Their plasticity at room temperature increased and melting poit (Tm) decreased along with the content of plasticizer increasing. Besides, a unique morphology existed in the PLA porous membrane can be obtained by adding PEG. PLA increase or decrease the molecular weight of PEG PEG content submitted /PEG membrane porosity. When PLA/PEG ratio was 8:2 (W/W) and PEG molecular weight was 400, microporous membranes have a porous structure of a regular, highly interconnected.PLA/PEG 400 (8:2, w/w) microporous membrane were successfully fabricated and activated with glutaraldehyde (GA) to interact with enzyme molecules. A lipase isolated from Candida rugosa (Type VII) was employed as a model biocatalyst and successfully immobilized onto the membrane surfaces via covalent bonds with the aldehyde groups. Optimal immobilization conditions by orthogonal test, measured under optimal conditions, the PLA/PEG membrane reached the highest enzyme activity at 25.11±0.95 U/g of the membrane and Lipase loading at 7.41+0.24 mg/g membrane. Effect of immobilization conditions on lipase’s activity was investigated. Some people think, pH values of tolerance, after chemical fixed thermal and storage stability of lipase lipase significantly improved. Furthermore, the immobilized lipase can be easily recovered and kept at 81% of its initial activity of which is used to FOT5 times. Thus, glutaraldehyde activated PLA/PEG film is a promising solid-phase enzyme-immobilized support medium, and the immobilized enzymes could have broad biocatalytic applications.