White spots and gaps of microbial single cell proteins for food applications: yeasts, bacteria and filamentous fungi.

This review comprehensively evaluates microbial single cell proteins (SCPs) including yeasts, bacteria and filamentous fungi as sustainable and high-quality protein sources for future food systems. Adopting a multidisciplinary perspective, it identifies key research gaps and white spots along the entire value chain, from production to consumer acceptance. Yeast-based SCPs are the most advanced, with established protein ingredients or biomasses and broad functional potential, while filamentous fungi show strong relevance for meat analogues due to their inherent structuring properties. In contrast, bacterial SCPs, despite their production advantages regarding high growth rate and yield, remain underexplored for food applications, largely due to limited ingredient availability and regulatory barriers. A common hurdle for all SCPs is upscaling due to technological and infrastructural barriers eventually hindering cost-efficient production. Furthermore, food safety concerns and missing knowledge on matrix effects in complex food products beyond simple model systems slow down product development and market launches. Additional gaps exist in standardized sustainability assessments, safety evaluation, and consumer perception across various demographics and food types. Overall, single cell protein (SCP) represents a highly promising but unevenly developed protein platform. Unlocking their full potential will require interdisciplinary insights and advances in process engineering, food design, nutrition science, sustainability metrics, and consumer research to enable safe, functional, and widely accepted food applications.