Department of Molecular Biosciences & Bioengineering, University of Hawaii, 1955 Eastwest Rd., Agricultural Science 218, Honolulu, HI 96822, United States.
J Biotechnol. 2010 Jul 20;148(2-3):119-27. doi: 10.1016/j.jbiotec.2010.05.001. Epub 2010 May 24.
Glucoamylase and alpha-amylase co-immobilized with gamma ferric oxide powders in chitosan beads for consecutive starch liquefaction and saccharification under different magnetic fields was investigated. The chitosan concentration in the beads was found to greatly affect the immobilized enzyme performance. Superior immobilization efficiency and enzyme stability were noted when 2% instead of 4% chitosan was utilized. Using confocal microscopy and scanning electron microscopy, the beads with 2% chitosan were seen to exhibit a more rugged surface topology with more macropores and accommodate more protein near the external surface than with the 4% chitosan beads. An optimum loading ratio between alpha-amylase and glucoamylase exists that gives the highest glucose production, and this ratio varies with the size of the beads. The inclusion of the gamma ferric oxide powders renders the beads magnetically anisotropic and causes them to tumble under a single-phase alternating magnetic field, resulted in increased overall reaction rates. When exposed to a three-phase alternating magnetic field, these beads were stirred vigorously, also leading to enhanced reaction rates. The use of multi-enzyme co-immobilization in magnetic anisotropic chitosan beads may be extended to other practical applications that involve coordinated enzymatic reactions of macromolecular substrates.
用γ-氧化铁粉末将糖化酶和α-淀粉酶共固定在壳聚糖珠中，在不同磁场下连续进行淀粉液化和糖化反应。发现壳聚糖珠中壳聚糖的浓度对固定化酶的性能有很大的影响。当使用 2%壳聚糖而不是 4%壳聚糖时，固定化效率和酶稳定性都更高。通过共聚焦显微镜和扫描电子显微镜观察，发现 2%壳聚糖珠的表面拓扑结构更加崎岖，具有更多的大孔，并且在外部表面附近容纳更多的蛋白质，而 4%壳聚糖珠则没有。α-淀粉酶和糖化酶之间存在最佳的负载比例，可获得最高的葡萄糖产量，而且这个比例随珠粒大小而变化。γ-氧化铁粉末的加入使珠粒具有各向异性磁，在单相交流磁场下使珠粒翻滚，从而提高了整体反应速率。当暴露于三相交流磁场时，这些珠粒被剧烈搅拌，也导致反应速率提高。在各向异性壳聚糖珠中使用多酶共固定化的方法可以扩展到其他涉及大分子底物协调酶反应的实际应用中。
