Solid-State Fermentation Towards Sustainability and Circularity in the Bioprocessing of Agri-Food Industrial Wastes

Solid-state fermentation (SSF) is a pivotal biotechnology in the circular economy, leveraging agri-food industrial waste and byproducts to produce high-value bioproducts while minimizing organic waste. By aligning with sustainability goals and zero-waste principles, SSF enables the production of enzymes, bioactive compounds, and secondary metabolites for food, agriculture, and biomedical applications. Recent advancements have optimized critical parameters, including substrate selection, culture conditions, and scalable bioreactor designs, enhancing process efficiency and reducing environmental impact. Despite progress, challenges persist in maximizing production yields and fostering industrial adoption. Addressing these hurdles, particularly through integrated environmental and techno-economic analyses, is essential to solidify SSF's role as a sustainable and competitive bioprocessing method. This review analyzes the latest advances in SSF, including the valorization of food and agro-industrial wastes, innovative bioreactor designs, microbial engineering for more efficient strains, bioenergy production and its integration into biorefineries, and contributions to the circular bioeconomy. Thus, SSF emerges as a key technology in sustainable industrial biotechnology, offering eco-friendly alternatives and promoting a more efficient production model.