Lipase Immobilization On Novel Mesoporous Silica Materials And Their Catalytic Performance

Mesoporous silica materials have extensively been used for the immobilization of enzymes.Mesoporous silicas are promising candidates for enzyme immobilization with respect to the requirements of enzyme carriers such as large surface area,narrow pore size distribution,the thermal and mechanical stability and toxicological safety.In this study,Burkholderia cepacia lipase(BCL)and Lipase B from C.Antarctica(CALB)were chosen as model enzymes,and mesoporous silica materials were chosen as supports for lipase immobilization using physical adsorption and cross-linking methods.The details in this study were summarized as follows:(1)Mesoporous silica nanoparticles were synthesized by using tannic acid as pore-forming agent,which is an environmentally friendly,cheap and non-surfactant template.SEM,TEM images and DLS results indicated that the tannic acid-templated mesoporous silica nanoparticles(TA-MSNs)are monodisperse spherical-like particles with an average diameter of 195±16 nm.BET results showed that the TA-MSNs had a relative high surface area(447 m~2/g),large pore volume(0.91 cm~3/g)and the mean pore sizes was ca.10.1 nm.BCL was immobilized on the TA-MSNs by physical adsorption for the first time and the properties of immobilized lipase(BCL@TA-MSNs)were investigated.The BCL@TA-MSNs exhibited satisfactory thermal stability,strong tolerance to organic solvents such as methanol,ethanol,isooctane,n-hexane and tetrahydrofuran,and high operational stability when BCL@TA-MSNs was applied in esterification and transesterification reactions.After recycling 10 times in the esterification reaction,over 71.4%of the initial enzyme activity can be maintained.After recycling 15 times in the transesterification reaction for biodiesel production,over 85%of biodiesel yield can be achieved.With these desired characteristics,TA-MSNs may be excellent candidates for enzymes immobilization.(2)Lipase B from C.antarctica(CALB)was immobilized on TA-MSNs.Changing the order of the addition of glutaraldehyde(GA)and CALB,and examining the enzyme activity to determine which reagent should be added first.The results showed that when GA is absorbed prior to lipase,the immobilized enzyme(GA-CALB@TA-MSNs)owns higher enzyme activity.The properties of the immobilized lipase were investigated.The GA-CALB@TA-MSNs exhibited satisfactory thermal stability,strong tolerance to organic solvents such as methanol,isooctane,n-hexane and tetrahydrofuran,and high reusability when the immobilized lipase was applied in esterification reactions.After recycling 10 times in the esterification reaction,over 84.8%of the conversion of the oleic acid can be maintained when CALB@TA-MSNs were used as catalyst,and over 94.3%of the oleic acid conversion can be maintained when GA-CALB@TA-MSNs were used as catalysts.(3)The uniform monodispersed dendritic mesoporous silica nanospheres(D-MSNs)were synthesized by using hexadecyl trimethyl ammonium chloride(CTAC)as template,triethanol amine(TEA)as catalyst and tetraethyl orthosilicate(TEOS)as silica precursor.SEM and TEM images indicated that the D-MSNs are monodispersed spherical particles with an average diameter of 177±14 nm.BET results showed that the TA-MSNs had a relative high surface area(462 m~2/g),large pore volume(0.91 cm~3/g)and the mean pore sizes was ca.10.67 nm.CALB was immobilized on the D-MSNs by physical adsorption for the first time and the properties of immobilized lipase(CALB@D-MSNs)were investigated.The CALB@D-MSNs exhibited satisfactory thermal stability,strong tolerance to organic solvents,and high operational stability when it was applied in esterification reactions.After recycling10 times in the esterification reaction,more than 85.1%of the oleic acid conversioncan be maintained.