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By 2050, the global demand for nutritional protein will increase by about 50%. Yet, the boundaries of environmental sustainability are already severely trespassed in the traditional fertilizer-feed-food chain and in fish-meal based aquaculture. Around the world, researchers have taken up the quest for novel, sustainable protein foods. Recovering and recycling renewable resources from waste streams is one of the key steps to mitigate the environmental impact. In single cell protein (SCP) production, both societal needs perfectly match, as microbial technology is probably the most resource-efficient manner of producing nutritional protein. In this new era of (meta)transcriptomics and (meta)proteomics, we start to see a glimpse of all the biological features that can be steered. This provides a strong incentive to revisit SCP, for the first time with a fundamental and mechanistically driven approach, exploiting not only the potential of a microbial cell to its fullest, but also the even richer genetic pool of a microbial community. Purple non-sulfur bacteria (PNSB) are nutritionally one of the most attractive types of SCP, and are furthermore metabolically the most versatile organisms on the planet. Each type of (sub)metabolism represents distinct (meta)proteomes, and hence nutritional properties such as essential amino acid profile, gastro-intestinal digestibility and nucleic acid content. Biotechnologically, the controllability of autotrophically grown PNSB communities is completely unexplored. A set of 9 tools has been distilled from a number of biological and ecological response mechanisms. In brief, it is hypothesized based on recent proteomic data that different cellular responses can yield drastically different essential amino acid (EAA) profiles (directly links to proteome), digestibility (membrane properties and subcellular protein distribution) and RNA pool (directly links to transcriptome and activity status of the cell). The goal is to exploit this to its fullest, with radical switches in the energy source as most ambitious tool based on hydrogen gas. It is envisaged to graft on a core anaerobic phototrophic metabolism switches back and forth to aerobic dark. At the level of the microbial community, the objective is to synergistically make use of the full richness of the metaproteome and metatranscriptome of several PNSB and non-PNSB populations. This translates into the development of tools that can very selectively control microbial competition
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