Azotobacter vinelandii is an obligate aerobic diazotroph with verified transient capability to reduce carbon monoxide to ethylene by its vanadium nitrogenase. In this study, we implemented an industrially relevant continuous two-stage stirred-tank system for in vivo biotransformation of a controlled supply of air enriched with 5% carbon monoxide to 302 μg ethylene g^-1 glucose consumed. To attain this value, the process required overcoming critical oxygen limitations during cell proliferation while simultaneously avoiding the A. vinelandii respiratory protection mechanism that negatively impacts in vivo nitrogenase activity. Additionally, process conditions allowed for the demonstration of carbon monoxide's solubility as a reaction-limiting factor and a competitor with dinitrogen for the vanadium nitrogenase active site; implying that excess intracellular carbon monoxide could lead to a cessation of cell proliferation and ethylene formation as shown genetically using a new strain of A. vinelandii deficient in carbon monoxide dehydrogenase.

IMPORTANCE Ethylene is an essential commodity feedstock used for the generation of a variety of consumer products, but its generation demands energy intensive processes and is dependent on nonrenewable substrates. This work describes a continuous biological method for investigating the nitrogenase-mediated carbon monoxide reductive coupling involved in ethylene production using whole cells of Azotobacter vinelandii. If eventually adopted by industry, this white technology has the potential to significantly lower the total energy inputs, ethylene recovery costs, as well as decreasing greenhouse gas emissions associated with current production strategies.

葡萄固氮菌是专性有氧重氮营养菌，具有经证实的通过其钒固氮酶将一氧化碳还原成乙烯的瞬时能力。在这项研究中，我们实施了工业上相关的连续两阶段搅拌罐系统，以对富含5％一氧化碳的受控供应的空气进行体内生物转化，以消耗302μg乙烯g ^-1葡萄糖。为了获得该值，该过程需要克服细胞增殖过程中的关键氧限制，同时避免对体内产生负面影响的A. vinelandii呼吸保护机制固氮酶活性。此外，工艺条件还可以证明一氧化碳的溶解度是反应限制因子，是钒氮酶活性位点与二氮的竞争剂。暗示过量的细胞内一氧化碳可能导致细胞增殖的停止和乙烯的形成，如使用一氧化碳脱氢酶缺乏的新菌株A. vinelandii遗传显示的那样。

重要信息乙烯是用于生产各种消费品的重要商品原料，但其生产需要能源密集型过程，并且依赖于不可再生的底物。这项工作描述了一种连续的生物学方法，用于研究使用葡萄固氮菌的整个细胞进行的涉及乙烯生产的固氮酶介导的一氧化碳还原偶联。如果最终被工业采用，则这种白色技术有可能显着降低总能量输入，乙烯回收成本以及减少与当前生产策略相关的温室气体排放。