用吸附法固定脂肪酶时,膜材料的亲疏水性对固定化酶的量、比活力和活力稳定性等有很大影响.今以柱状假丝酵母脂肪酶和猪胰脂肪酶为研究对象,选取了8种亲疏水性不同的膜材料（醋酸纤维素、聚丙烯腈、聚酰胺、聚砜、聚醚砜、聚偏二氟乙烯、聚丙烯和聚四氟乙烯）作为固定化载体,用吸附法制备了固定化脂肪酶膜.研究结果表明,强疏水性聚四氟乙烯和聚丙烯膜对两种酶的吸附量都比较大,且固定化酶的比活力和活力回收率比较高,聚四氟乙烯固定化柱状假丝酵母酶比游离态酶的半衰期提高了6倍以上.强亲水性醋酸纤维素膜对猪胰脂肪酶的吸附量比聚四氟乙烯高,但是固定化酶的比活力、活力回收率比强疏水性膜低,而接触角在40°～50°的聚酰胺膜和聚砜膜的吸附量最小.因此吸附法制备固定化脂肪酶膜,选择聚丙烯膜和聚四氟乙烯膜是合适的,制备的优化条件为吸附温度25℃,酶溶液的pH为7.5,吸附时间10 h.
Preparation of a novel coating is one of the keys to solid phase microextraction.A new method was proposed to prepare a chitosan microprobe with a film thickness of several dozen micrometers with the phase inverse technique by using a microporous polyacrylonitrile (PAN) hollow fiber with a diameter of 1.5 mm as template.The dilute acetic acid solution of chitosan and glutaraldehyde was added into the hollow fiber, a quartz fiber was inserted into the hollow fiber as supporter and then the hollow fiber was placed in the NaOH solution, because of the porosity of hollow fiber, NaOH diffused and contacted with acetic acid, then the chitosan thin film was formed.For intensifying the adsorption of acidic compounds, the probe was then modified with polyethyleneiminate (PEI).The SEM photos showed that the probe obtained with this process was 17 μm thick.The PEI-modified chitosan probes showed stronger adsorption of furomeside.Using NaOH as desorber, a concentration factor over 10 was observed and the solute concentration in the desorber was linear with that in the original samples.The operation is convenient and easy to realize automation.
Three kinds of support for enzyme immobilization were prepared by modifying SBA-15 mesoporous silica with thiol,methyl and hexyl groups respectively.The prepared supports were characterized with FT-IR and BET method and exhibited high specific surface area and uniform pore size.Furthermore,unmodified SBA-15 and the modified SBA-15 materials were used for lipase immobilization.The results were compared in terms of enzyme adsorption capacity,activity,activity retention and stability.The modified SBA-15 materials with thiols(SBA-15-PrSH)showed good performance for lipase immobilization.Compared with unmodified SBA-15,the adsorption capacity of SBA-15-PrSH to lipase was improved by more than 80%,and the activity retention increased by more than 10%.
