Candida antarctica lipase B chemically immobilized on epoxy-activated micro- and nanobeads:: Catalysts for polyester synthesis
Candida antarctica lipase B chemically immobilized on epoxy-activated micro- and nanobeads:: Catalysts for polyester synthesis
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DOI：
10.1021/bm700949x
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发表时间：
2008-02-01
影响因子：
6.2
通讯作者：
Gross, Richard A.
中科院分区：
文献类型：
--
作者：
Chen, Bo;Hu, Jun;Gross, Richard A.
将南极假丝酵母脂肪酶B（CALB）共价固定到环氧活化的大孔聚（甲基丙烯酸甲酯）Amberzyme珠（235 μ m粒径，220埃孔径）和具有聚（甲基丙烯酸缩水甘油酯）外部区域的纳米颗粒（nanoPSG，直径68 nm）上。Amberzyme珠粒允许CALB负载高达0.16g酶/克支持物。Amberzyme-CALB珠的IR显微光谱产生的图像显示CALB定位在50 μ m厚的装载前沿内。在用DMSO/Triton X-100水溶液处理Amberzyme-CALB之前和之后记录的IR显微光谱图像是相似的，证实CALB在很大程度上与Amberzyme化学连接。固定在Amberzyme，Lewatit（即，Novozym 435催化剂）和nanoPSG进行内酯开环和逐步缩合聚合。例如，使用Amberzym-CALB、Novozym 435和nanoPSG-CALB催化20分钟的相同量的酶，ε-己内酯的转化百分比分别为7.0%、16%和65%。基于树脂的物理参数和活性位点滴定法测定的活性位点的可用性，讨论了CALB反应性的差异。无论使用的基质和化学与物理固定，ε-CL开环聚合发生的链增长机制没有链终止。为了测试Amberzyme-CALB稳定性，将催化剂重复使用三个反应循环用于ε-CL开环聚合（70 ℃，70分钟反应）和甘油/1，8-辛二醇/己二酸缩聚反应（90 ℃，64小时）。发现Amberzyme-CALB相对于Novozym 435对于缩聚反应具有更好的重复使用稳定性。
Candida antarctica Lipase B (CALB) was covalently immobilized onto epoxy-activated macroporous poly(methyl methacrylate) Amberzyme beads (235 mu m particle size, 220 angstrom pore size) and nanoparticles (nanoPSG, diameter 68 nm) with a poly(glycidyl methacrylate) outer region. Amberzyme beads allowed CALB loading up to 0.16 g of enzyme per gram of support. IR microspectroscopy generated images of Amberzyme-CALB beads showed CALB is localized within a 50 mu m thick loading front. IR microspectroscopy images, recorded prior to and after treatment of Amberzyme-CALB with DMSO/aqueous Triton X-100, are similar, confirming-that CALB is largely chemically linked to Amberzyme. The activity of CALB immobilized on Amberzyme, Lewatit (i.e., Novozym 435 catalyst), and nanoPSG was assessed for lactone ring-opening and step-condensation polymerizations. For example, the percent conversion of epsilon-caprolactone using the same amount of enzyme catalyzed by Amberzym-CALB, Novozym 435, and nanoPSG-CALB for 20 min was 7.0, 16, and 65%, respectively. Differences in CALB reactivity were discussed based on resin physical parameters and availability of active sites determined by active site titrations. Regardless of the matrix used and chemical versus physical immobilization, epsilon-CL ring-opening polymerizations occur by a chain growth mechanism without chain termination. To test Amberzyme-CALB stability, the catalyst was reused over three reaction cycles for epsilon-CL ring-opening polymerization (70 degrees C, 70 min reactions) and glycerol/1,8-octanediol/adipic acid polycondensation reactions (90 degrees C, 64 h). Amberzyme-CALB was found to have far better stability for reuse relative to Novozym 435 for the polycondensation reaction.