Department of Applied Molecular Bioscience, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Japan.
Biotechnol Prog. 2010 Jul-Aug;26(4):1047-53. doi: 10.1002/btpr.409.
Formate dehydrogenase from Candida boidinii (CbFDH) is potentially applicable in reduction of CO(2) through oxidation of cofactor NADH into NAD(+). For this, the CbFDH activity needs to be maintained under practical reaction conditions, such as CO(2) gas-liquid flow. In this work, CbFDH and cofactor were encapsulated in liposomes and the liposomal enzymes were characterized in an external loop airlift bubble column. The airlift was operated at 45 degrees C with N(2) or CO(2) as gas phase at the superficial gas velocity U(G) of 2.0 or 3.0 cm/s. The activities of liposomal CbFDH/cofactor systems were highly stable in the airlift regardless of the type of gas phase because liposome membranes prevented interactions of the encapsulated enzyme and cofactor molecules with the gas-liquid interface of bubbles. On the other hand, free CbFDH was deactivated in the airlift especially at high U(G) with CO(2) bubbles. The liposomal CbFDH/NADH could catalyze reduction of CO(2) in the airlift giving the fractional oxidation of the liposomal NADH of 23% at the reaction time of 360 min. The cofactor was kept inside liposomes during the reaction operation with less than 10% of leakage. All of the results obtained demonstrate that the liposomal CbFDH/NADH functions as a stable catalyst for reduction of CO(2) in the airlift.
毕赤酵母(formate dehydrogenase from Candida boidinii, CbFDH)在氧化辅因子 NADH 的同时将 CO2还原为 NAD+，具有将 CO2转化为有价值化学品的应用潜力。为了实现这一目标，需要在实际反应条件下（如 CO2气液流动）保持 CbFDH 的活性。在这项工作中，将 CbFDH 和辅因子包封在脂质体中，并在外部环式空气提升鼓泡塔中对脂质体酶进行了表征。在 45℃下，以 N2或 CO2为气相，在表观气速 U(G)为 2.0 或 3.0 cm/s 的条件下操作空气提升。无论气相类型如何，脂质体 CbFDH/辅因子系统的活性在空气提升中都非常稳定，因为脂质体膜阻止了包封的酶和辅因子分子与气泡气液界面的相互作用。另一方面，游离的 CbFDH 在空气提升中特别是在高 U(G)和 CO2气泡下失活。脂质体 CbFDH/NADH 可以在空气提升中催化 CO2的还原，在 360 min 的反应时间内，脂质体 NADH 的氧化分数为 23%。在反应过程中，辅因子保留在脂质体内部，泄漏率小于 10%。所有结果表明，脂质体 CbFDH/NADH 作为空气提升中 CO2还原的稳定催化剂发挥作用。
