Department of Chemical Engineering and Biotechnology, Ariel University Center of Samaria, Ariel 40700, Israel.
J Biotechnol. 2011 May 20;153(3-4):138-44. doi: 10.1016/j.jbiotec.2011.03.026. Epub 2011 Apr 8.
Formaldehyde (FA)-containing indoor air has a negative effect on human health and should be removed by intensive ventilation or by catalytic conversion to non-toxic products. FA can be oxidized by alcohol oxidase (AOX) taking part in methanol metabolism of methylotrophic yeasts. In the present work, AOX isolated from a Hansenula polymorpha C-105 mutant (gcr1 catX) overproducing this enzyme in glucose medium, was tested for its ability to oxidize airborne FA. A continuous fluidized bed bioreactor (FBBR) was designed to enable an effective bioconversion of airborne FA by AOX or by permeabilized mutant H. polymorpha C-105 cells immobilized in calcium alginate beads. The immobilized AOX having a specific activity of 6-8 U mg⁻¹ protein was shown to preserve 85-90% of the initial activity. The catalytic parameters of the immobilized enzyme were practically the same as for the free enzyme (k(cat)/K(m) was 2.35×10³ M⁻¹ s⁻¹ vs 2.89×10³ M⁻¹ s⁻¹, respectively). The results showed that upon bubbling of air containing from 0.3 up to 18.5 ppm FA through immobilized AOX in the range of 1.3-26.6 U g⁻¹ of the gel resulted in essential decrease of FA concentration in the outlet gas phase (less than 0.02-0.03 ppm, i.e. 10-fold less than the threshold limit value). It was also demonstrated that a FBBR with immobilized permeabilized C-105 cells provided more than 90% elimination of airborne FA. The process was monitored by a specially constructed enzymatic amperometric biosensor based on FA oxidation by NAD+ and glutathione-dependent formaldehyde dehydrogenase from the recombinant H. polymorpha Tf 11-6 strain.
甲醛（FA）含量高的室内空气会对人体健康造成负面影响，需要通过强化通风或催化转化为无毒产物来去除。FA 可以通过参与甲醇代谢的甲醇营养型酵母中的醇氧化酶（AOX）氧化。在本工作中，从产酶能力强的汉逊酵母 C-105 突变株（gcr1 catX）中分离出的 AOX 在葡萄糖培养基中被用于氧化空气中的 FA。为了有效地通过 AOX 或固定在海藻酸钙珠中的渗透化突变汉逊酵母 C-105 细胞进行空气 FA 的生物转化，设计了一个连续流流化床生物反应器（FBBR）。固定化 AOX 的比活度为 6-8 U mg⁻¹ 蛋白，初始活性保持在 85-90%。固定化酶的催化参数与游离酶基本相同（k(cat)/K(m)分别为 2.35×10³ M⁻¹ s⁻¹ 和 2.89×10³ M⁻¹ s⁻¹）。结果表明，当空气以 0.3 至 18.5 ppm FA 的浓度通过 1.3-26.6 U g⁻¹ 凝胶固定的 AOX 鼓泡时，出口气相中的 FA 浓度显著降低（小于 0.02-0.03 ppm，即比阈值限值低 10 倍）。此外，用固定化的渗透化 C-105 细胞的 FBBR 可以提供超过 90%的空气 FA 消除。该过程通过基于 FA 氧化的 NAD+和谷胱甘肽依赖的甲醛脱氢酶的特殊构建的酶安培生物传感器进行监测，该酶来自重组汉逊酵母 Tf 11-6 菌株。
