Purple photosynthetic bacteria are a class of anoxygenic phototrophic bacteria that use sunlight as an energy source; they are not oxygen producers. Cyanobacteria and algae, however, can produce oxygen photogenically. Instead, purple bacteria can fix carbon dioxide using organic and inorganic electron donors in the sunlight with or without oxygen presence. This flexible metabolism allows them to use different energy sources. Their remarkable ability to switch between trophic systems differs from other microbes, where they do not rely on oxygen and can even grow in the dark. As a result, purple bacteria can efficiently produce high amounts of biomass with low maintenance needs. This makes them suitable for wastewater treatment and resource recovery applications. Their versatile abilities also provide opportunities to produce valuable chemicals and commodities. Areas of focus include biohydrogen, bioplastics, and nutrients, such as vitamins and coenzymes. Purple bacteria can synthesize polyhydroxyalkanoates for renewable energy storage and bioplastics. They also produce proteins, pigments, and isoprenoids used in nutrition, fragrances, and biofuels. Optimized enzymes also allow hydrogen gas production for fuel. Purple bacteria's diverse metabolic capabilities and efficient photosynthesis provide many potential environmental and industrial uses. Herein, we will review the latest applications and their environmental impacts.