Harnessing the metabolic versatility of purple non-sulfur bacteria

A transition to a circular economy is necessary to mitigate the negative effects on the environment of the exploitation and disposal of materials and to achieve society-wide benefits. The current produce-waste-dispose model is slowly changing toward a more sustainable produce-userecycle- upcycle model. In this context, bio-based processes using microbial mixed cultures are crucial to develop waste-to-resource valorization processes.
Purple phototrophic bacteria (PPB) form a guild of hyper-versatile organisms found in almost all aqueous environments, thriving on infrared light energy, capturing organics by photoorganoheterotrophy, and even recycling CO2 by photolithoautotrophy. Due to their outstanding metabolic versatility, their organic and nutrient capture ability, and their biomass yields over substrate approaching 1 g CODx g-1 CODs, PPB are dedicated organisms to study and use for the development of water resource recovery applications. Despite already 80 years of research on PPB, their physiology still needs to get deciphered, and their environmental biotechnological exploitation is at its infancy.
The aim of this thesis was to study and harness the metabolic versatility of PPB at different levels, from the elucidation of light-driven physiologies in pure cultures to the management of selection phenomena, population dynamics, and distributed metabolic functionalities in mixed cultures. The findings were aggregated to derive to mixed-culture bioprocess application perspectives for capturing organics and nutrients from municipal sewage and agri-food wastewater and producing valuable products, as bioplastics, biohydrogen or photopigments. In this thesis, a comprehensive overview of the potential of PPB for water resource recovery is given. The molecular principles and ecological dynamics governing the PPB metabolism were elucidated with the goal to demonstrate the potential of PPB-based biotechnologies.