Abstract: The swiftly growing population and climate change present a significant danger to our existing food systems. Additionally, the extensive reliance on animal-derived and plant-derived protein presents disadvantages, as these food sources demand significant land and water, are subject to seasonal fluctuations, incur high costs, and lead to environmental pollution. Single-cell proteins (SCPs) are attracting significant research attention because of their impressive characteristics, including protein content comparable to other sources; minimal land and water requirements; reduced carbon footprint; and a brief production timeframe. This examination investigates the utilization of food waste as an eco-friendly feedstock for the progression of SCP processes. It examines SCP research that utilizes food waste as a substrate, along with the biocatalysts (bacteria, fungi, yeast, and microalgae) employed. The operational setpoint conditions that regulate SCP yields and SCP fermentation pathways are also clarified. This assessment also illustrates the application of the biorefinery concept in literature to enhance the economic viability of "waste-to-protein" innovations, resulting in the creation of multiproduct value chains. A brief part that examines the Researcher SCP situation is included as well. The technical and financial challenges encountered by second-generation SCP processes are examined, along with future outlooks. Consequently, SCP technologies may significantly contribute to fast-tracking a "sustainable protein market" and addressing the worldwide hunger emergency.

Keywords: Biorefinery concept, SCP-Producing Microbes, Single-Cell Protein Production, Single-cell proteins (SCPs), Solid-State Fermentation.