Biocatalytic oxidation is an interesting prospect for the selective synthesis of active pharmaceutical intermediates. Bubbling air or oxygen is considered as an efficient method to increase the gas–liquid interface and thereby enhance oxygen transfer. However, the enzyme is deactivated in this process and needs to be further studied and understood to accelerate the implementation of oxidative biocatalysis in larger production processes. This paper reports data on the stability of NAD(P)H oxidase (NOX) when exposed to different gas–liquid interfaces introduced by N₂ (0% oxygen), air (21% oxygen), and O₂ (100% oxygen) in a bubble column. A pH increase was observed during gas bubbling, with the highest increase occurring under air bubbling from 6.28 to 7.40 after 60 h at a gas flow rate of 0.15 L min^–1. The kinetic stability of NOX was studied under N₂, air, and O₂ bubbling by measuring the residual activity, the deactivation constants (k_d1) were 0.2972, 0.0244, and 0.0346 with the corresponding half-lives of 2.2, 28.6, and 20.2 h, respectively. A decrease in protein concentration of the NOX solution was also observed and was attributed to likely enzyme aggregation at the gas–liquid interface. Most aggregation occurred at the air–water interface and decreased greatly from 100 to 14.16% after 60 h of bubbling air. Furthermore, the effect of the gas–liquid interface and the dissolved gas on the NOX deactivation process was also studied by bubbling N₂ and O₂ alternately. It was found that the N₂–water interface and O₂–water interface both had minor effects on the protein concentration decrease compared with the air–water interface, whilst the dissolved N₂ in water caused serious deactivation of NOX. This was attributed not only to the NOX unfolding and aggregation at the interface but also to the N₂ occupying the oxygen channel of the enzyme and the resultant inaccessibility of dissolved O₂ to the active site of NOX. These results shed light on the enzyme deactivation process and might further inspire bioreactor operation and enzyme engineering to improve biocatalyst performance.

中文翻译：

---

氮气、空气和氧气对暴露于气液界面的 NAD(P)H 氧化酶动力学稳定性的影响,氮气、空气和氧气对暴露于气液界面的 NAD(P)H 氧化酶动力学稳定性的影响

生物催化氧化是选择性合成活性药物中间体的一个有趣的前景。鼓泡空气或氧气被认为是增加气液界面从而增强氧气传递的有效方法。然而，酶在此过程中失活，需要进一步研究和了解，以加速氧化生物催化在更大生产过程中的实施。_{本文报告了 NAD(P)H 氧化酶 (NOX) 暴露于由 N 2}（0% 氧气）、空气（21% 氧气）和 O ₂引入的不同气液界面时的稳定性数据（100% 氧气）在鼓泡塔中。在气体鼓泡过程中观察到 pH 值增加，在气体流速为 0.15 L min ^–1的情况下，60 小时后，在空气鼓泡下，pH 值增加最高，从 6.28 升至 7.40 。通过测量残余活性、失活常数（k _{d1 ）}，研究了在 N ₂、空气和 O _{2鼓泡下 NOX 的动力学稳定性。}）分别为 0.2972、0.0244 和 0.0346，相应的半衰期分别为 2.2、28.6 和 20.2 小时。还观察到 NOX 溶液的蛋白质浓度下降，这可能是由于气液界面处的酶聚集所致。大多数聚集发生在空气-水界面，鼓泡空气 60 小时后，聚集从 100% 大幅下降至 14.16%。_{此外，通过交替通入N 2}和O ₂，​​研究了气液界面和溶解气体对NOX失活过程的影响。结果发现，与空气-水界面相比，N ₂ -水界面和O ₂ -水界面对蛋白质浓度降低的影响较小，而溶解的N ₂水中的氮氧化物会导致严重失活。这不仅归因于NOX在界面处解折叠和聚集，还归因于N ₂占据了酶的氧通道，导致溶解的O ₂无法接近NOX的活性位点。这些结果揭示了酶失活过程，并可能进一步启发生物反应器操作和酶工程以提高生物催化剂的性能。,生物催化氧化是选择性合成活性药物中间体的一个有趣的前景。鼓泡空气或氧气被认为是增加气液界面从而增强氧气传递的有效方法。然而，酶在此过程中失活，需要进一步研究和了解，以加速氧化生物催化在更大生产过程中的实施。_{本文报告了 NAD(P)H 氧化酶 (NOX) 暴露于由 N 2}（0% 氧气）、空气（21% 氧气）和 O ₂引入的不同气液界面时的稳定性数据（100% 氧气）在鼓泡塔中。在气体鼓泡过程中观察到 pH 值增加，在气体流速为 0.15 L min ^–1的情况下，60 小时后，在空气鼓泡下，pH 值增加最高，从 6.28 升至 7.40 。通过测量残余活性、失活常数（k _{d1 ）}，研究了在 N ₂、空气和 O _{2鼓泡下 NOX 的动力学稳定性。}）分别为 0.2972、0.0244 和 0.0346，相应的半衰期分别为 2.2、28.6 和 20.2 小时。还观察到 NOX 溶液的蛋白质浓度下降，这可能是由于气液界面处的酶聚集所致。大多数聚集发生在空气-水界面，鼓泡空气 60 小时后，聚集从 100% 大幅下降至 14.16%。_{此外，通过交替通入N 2}和O ₂，​​研究了气液界面和溶解气体对NOX失活过程的影响。结果发现，与空气-水界面相比，N ₂ -水界面和O ₂ -水界面对蛋白质浓度降低的影响较小，而溶解的N ₂水中的氮氧化物会导致严重失活。这不仅归因于NOX在界面处解折叠和聚集，还归因于N ₂占据了酶的氧通道，导致溶解的O ₂无法接近NOX的活性位点。这些结果揭示了酶失活过程，并可能进一步启发生物反应器操作和酶工程以提高生物催化剂的性能。