Ammonia (NH₃) is an important commodity chemical used as an agricultural fertilizer and hydrogen-storage material. There has recently been much interest in developing an environmentally benign process for NH₃ synthesis. Here, we report enhanced production of ammonia from diazotrophs under light irradiation using hybrid composites of inorganic nanoparticles (NPs) and bacterial cells. The primary focus of this study lies in the intracellular biosynthesis of semiconductor NPs within Azotobacter vinelandii, a diazotroph, when bacterial cells are cultured in a medium containing precursor molecules. For example, enzymes in bacterial cells, such as cysteine desulfurase, convert cysteine (Cys) into precursors for cadmium sulfide (CdS) synthesis when supplied with CdCl₂. Photoexcited charge carriers in the biosynthesized NPs are transferred to nitrogen fixation enzymes, e.g., nitrogenase, facilitating the production of ammonium ions. Notably, the intracellular biosynthesis approach minimizes cell toxicity compared to extracellular synthesis due to the diminished generation of reactive oxygen species. The biohybrid system based on the in vivo approach results in a fivefold increase in ammonia production (0.45 mg g_DCW⁻¹ h⁻¹) compared to the case of diazotroph cells only (0.09 mg g_DCW⁻¹ h⁻¹).

中文翻译：

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在 Azotobacter vinelandii 中体内合成半导体纳米颗粒用于光驱动氨生产


氨 （NH₃） 是一种重要的商品化学品，用作农业肥料和储氢材料。最近，人们对开发一种对环境无害的 NH₃ 合成工艺产生了浓厚的兴趣。在这里，我们报道了使用无机纳米颗粒 （NPs） 和细菌细胞的杂化复合材料在光照射下增强固氮营养生物的氨产生。本研究的主要重点在于当细菌细胞在含有前体分子的培养基中培养时，Azotobacter vinelandii（一种固氮营养菌）内半导体 NP 的细胞内生物合成。例如，当 CdCl₂ 提供时，细菌细胞中的酶（如半胱氨酸脱硫酶）会将半胱氨酸 （Cys） 转化为硫化镉 （CdS） 合成的前体。生物合成的 NP 中的光激发电荷载流子被转移到固氮酶（例如固氮酶）上，从而促进铵离子的产生。值得注意的是，由于活性氧的产生减少，与细胞外合成相比，细胞内生物合成方法最大限度地减少了细胞毒性。与仅固氮营养细胞的情况 （0.09 mg g_DCW ^{-1 h-1}） 相比，基于体内方法的生物杂交系统导致氨产生量增加五倍 （0.45 mg g_DCW ^-1 h ^-1）。