Oxidative stress in cells caused by the accumulation of reactive oxygen species (ROS) is a common cause of cell function degeneration, cell death and various diseases. Efficient, robust and inexpensive nanoparticles (nanoenzymes) capable of scavenging/detoxifying ROS even in harsh environments are attracting strong interest. Prussian blue analogues (PBAs), a prominent group of metalorganic nanoparticles (NPs) with the same cyanometalate structure as the traditional and commonly used Prussian blue (PB), have long been envisaged to mimic enzyme activities for ROS scavenging. However, their biological toxicity, especially potential effects on living beings during practical application, has not yet been fully investigated. Here we reveal the enzyme-like activity of FeCo-PBA NPs, and for the first time investigate the effects of FeCo-PBA on cell viability and growth. We elucidate the effect of the nanoenzyme on the ethanol-production efficacy of a typical model organism, the engineered industrial strain Saccharomyces cerevisiae. We further demonstrate that FeCo-PBA NPs have almost no cytotoxicity on the cells over a broad dosage range (0-100 μg mL-1), while clearly boosting the yeast fermentation efficiency by mitigating oxidative stress. Atmospheric pressure cold plasma (APCP) pretreatment is used as a multifunctional environmental stress produced by the plasma reactive species. While the plasma enhances the cellular uptake of NPs, FeCo-PBA NPs protect the cells from the oxidative stress induced by both the plasma and the fermentation processes. This synergistic effect leads to higher secondary metabolite yields and energy production. Collectively, this study confirms the positive effects of PBA nanoparticles in living cells through ROS scavenging, thus potentially opening new ways to control the cellular machinery in future nano-biotechnology and nano-biomedical applications.