Recycled agroindustrial waste has been of great interest during the last decade as a low-cost and sustainable substrate for fermentation processes. The types of products, yields, and potential applications depend mainly on the waste composition, which varies in terms of proteins, carbohydrates, and/or polyphenolic compounds. The most commonly reported microbial products are enzymes, pigments, biosurfactants, antibiotics, and phenolic compounds for different industrial applications. Advances in research on novel wastes as nutrient sources and the optimization of fermentation processes can help these materials transition from laboratory applications to an industrial level. This review explores reports published in the last five years (2017–2022) on different types of agroindustrial waste and their utilization in the production of useful microbial products. The present scenario and future scope of agroindustrial waste as substrates for submerged and solid-state fermentation processes are also discussed. The information was analyzed considering two main topics: (i) agroindustrial waste as substrates for fermentation processes and (ii) high-added value products obtained by microbial conversion. This review contributes to future research endeavors to discover the key factors that will allow us to reach the market with sustainable microbial products.

Potato waste was processed and used as a sole substrate for simultaneously producing antifungals and biopigments usingStreptomycesspp. Out of three differentStreptomycesisolates, strain SO6 stood out due to its ability to produce antifungals against economically important fungal phytopathogens and intracellular biopigments using potato waste powders without additional nutrients. This strain also showed the potential to secrete a broad range of enzymes for fermentation of eight sugars that could be involved in potato waste bioconversion. The results of the fermentation assay indicated thatStreptomycessp. strain SO6 degrades potato wastes during submerged fermentation, diminishing total dry weight and increasing reducing sugars from 0.3 to 3.6 mg·mL⁻¹and total proteins from 70.6 to 187.7 μg·mL⁻¹. The results showed thatStreptomycesstrain SO6 was able to convert the potato waste into 0.96 mg·g⁻¹of diffusible antifungals and 1.75 mg·g⁻¹of reddish-purple biopigments. On the contrary, an absence of pigment production was observed during the fermentation of the commercial medium used as reference. According to our results, replacement of commercial culture media with available low-cost agroindustrial wastes for producing bioactive chemicals is a real opportunity to enhance theStreptomycespigment production and antibiotic sustainability with cost-competitiveness. To our knowledge, this is the first report on the simultaneous production of biopigments and diffusible antifungal antibiotics produced byStreptomycesspp. using potato solid waste as the sole nutrient source.