Greco G, Alfani F, Iorio G, Cantarella M, Formisano A, Gianfreda L, Palescandolo R, Scardi V
Biotechnol Bioeng. 1979 Aug;21(8):1421-38. doi: 10.1002/bit.260210809.
Recently enzyme immobilization techniques have been proposed that are mainly founded on the formation of an enzyme-gel layer onto the active surface of an ultrafiltration membrane within an unstirred ultrafiltration cell. If the membrane molecular-weight cutoff is less than the enzyme molecular weight and hence such as to completely prevent enzyme permeation (once the enzyme solution has been charged into the test cell and pressure applied to the system), a time progressive increase in enzyme concentration takes place at the upstream membrane surface that can eventually lead to gelation and hence to enzyme immobilization. However, depending on the total enzyme amount fed, the maximum enzyme concentration achieved in the unsteady state could be less than the gelation level. In this situation, no immobilization occurs and the enzyme still remains in the soluble form although it is practically confined within a limited region immediately upstream the membrane and at fairly high concentrations. In this paper, the experimental conditions that allow gelling to occur are discussed together with a theoretical analysis of the soluble enzyme membrane reactor which is obtained when no gelling takes place. Such a system could be usefully employed in performing kinetic analyses at high enzyme concentration levels that are still in the soluble form.
最近有人提出了酶固定化技术，该技术主要基于在未搅拌的超滤池中，在超滤膜的活性表面上形成酶凝胶层。如果膜的截留分子量小于酶的分子量，从而能够完全阻止酶渗透（一旦将酶溶液装入测试池并对系统施加压力），则在膜上游表面会发生酶浓度随时间的逐渐增加，最终可能导致凝胶化，进而实现酶的固定化。然而，根据进料的总酶量，在非稳态下达到的最大酶浓度可能低于凝胶化水平。在这种情况下，不会发生固定化，尽管酶实际上被限制在膜上游紧邻的有限区域内且浓度相当高，但它仍保持可溶形式。本文讨论了允许发生凝胶化的实验条件，并对未发生凝胶化时得到的可溶性酶膜反应器进行了理论分析。这样的系统可有效地用于在仍为可溶形式的高酶浓度水平下进行动力学分析。
